U.S. patent application number 13/525330 was filed with the patent office on 2012-10-04 for gdf-15 and/or troponin t for predicting kidney failure in heart surgery patients.
This patent application is currently assigned to ROCHE DIAGNOSTICS OPERATIONS, INC.. Invention is credited to Georg Hess, Andrea Horsch, Dietmar Zdunek.
Application Number | 20120252035 13/525330 |
Document ID | / |
Family ID | 41506400 |
Filed Date | 2012-10-04 |
United States Patent
Application |
20120252035 |
Kind Code |
A1 |
Horsch; Andrea ; et
al. |
October 4, 2012 |
GDF-15 and/or Troponin T for Predicting Kidney Failure in Heart
Surgery Patients
Abstract
The present disclosure relates to the field of laboratory
diagnostics. Specifically, means and methods are disclosed for
determining a patient's risk of suffering from acute kidney injury
after a surgical procedure based on the detection of GDF-15,
troponin T and/or a natriuretic peptide.
Inventors: |
Horsch; Andrea; (Mannheim,
DE) ; Zdunek; Dietmar; (Tutzing, DE) ; Hess;
Georg; (Mainz, DE) |
Assignee: |
ROCHE DIAGNOSTICS OPERATIONS,
INC.
Indianapolis
IN
|
Family ID: |
41506400 |
Appl. No.: |
13/525330 |
Filed: |
June 17, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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PCT/EP2010/070058 |
Dec 17, 2010 |
|
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13525330 |
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Current U.S.
Class: |
435/7.1 ;
435/287.2 |
Current CPC
Class: |
G01N 2800/52 20130101;
G01N 2333/495 20130101; G01N 2333/52 20130101; G01N 33/6893
20130101; G01N 33/6863 20130101; G01N 2333/4712 20130101; G01N
2800/50 20130101; G01N 33/74 20130101; C07K 14/4716 20130101; G01N
2800/347 20130101 |
Class at
Publication: |
435/7.1 ;
435/287.2 |
International
Class: |
G01N 21/76 20060101
G01N021/76 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 18, 2009 |
EP |
09179925.4 |
Claims
1. A method for predicting a risk of acute kidney injury (AKI) in a
patient subjected to a surgical procedure, comprising: a)
contacting, in vitro, a sample obtained from the patient before the
patient undergoes the surgical procedure with a ligand comprising
specific binding affinity for GDF-15; b) determining the amount of
GDF-15 in the sample; and c) providing a prediction that the
patient is not at risk of AKI if the amount of GDF-15 is below
about 1078 pg/ml, or that the patient has an increased risk of AKI
if the amount of GDF-15 is above about 1717 pg/ml.
2. The method of claim 1, wherein the surgical procedure is
orthopedic surgery, a tumor resection, surgery of the
gastrointestinal tract not involving tumor resection, or cardiac
surgery.
3. The method of claim 1, wherein the ligand comprising specific
binding affinity for GDF-15 is an antibody, nucleic acid, receptor,
binding partner, or aptamer.
4. The method of claim 1, wherein the amount of GDF-15 in the
sample is determined by measuring a signal obtained from GDF-15,
wherein the intensity of the signal directly correlates with the
number of molecules of GDF-15 in the sample.
5. The method of claim 1, wherein the amount of GDF-15 in the
sample is determined by measuring a signal obtained from a
secondary component, wherein the intensity of the signal indirectly
correlates with the number of molecules of GDF-15 in the
sample.
6. The method of claim 1, wherein the patient is predicted to have
an increased risk of AKI requiring hemodialysis if the amount of
GDF-15 is above about 2573 pg/ml.
7. The method of claim 1, further comprising contacting, in vitro,
the sample obtained from the patient before the patient undergoes
the surgical procedure with a second ligand comprising specific
binding affinity for troponin T; determining the amount of troponin
T in the sample; and providing a prediction that the patient is not
at risk of AKI if the amount of GDF-15 is below about 1078 pg/ml
and the amount of troponin T is below about 13.3 pg/ml, or that the
patient has an increased risk of AKI if the amount of GDF-15 is
above about 1717 pg/ml and the amount of troponin T is above about
25.5 pg/ml.
8. The method of claim 1, further comprising contacting, in vitro,
the sample obtained from the patient before the patient undergoes
the surgical procedure with a second ligand comprising specific
binding affinity for NT-proBNP; determining the amount of NT-proBNP
in the sample; and providing a prediction that the patient is not
at risk of AKI if the amount of GDF-15 is below about 1078 pg/ml
and the amount of NT-proBNP is below about 488.2 pg/ml, or that the
patient has an increased risk of AKI if the amount of GDF-15 is
above about 1717 pg/ml and the amount of NT-proBNP is above about
1118.7 pg/ml.
9. The method of claim 1, further comprising contacting, in vitro,
the sample obtained from the patient before the patient undergoes
the surgical procedure with a second ligand comprising specific
binding affinity for troponin T and a third ligand comprising
specific binding affinity for NT-proBNP; determining the amounts of
troponin T and NT-proBNP in the sample; and providing a prediction
that the patient is not at risk of AKI if the amount of GDF-15 is
below about 1078 pg/ml, the amount of troponin T is below about
13.3 pg/ml, and the amount of NT-proBNP is below about 488.2 pg/ml;
or that the patient has an increased risk of AKI if the amount of
GDF-15 is above about 1717 pg/ml, the amount of troponin T is above
about 25.5 pg/ml, and the amount of NT-proBNP is above about 1118.7
pg/ml.
10. A method for predicting a risk of acute kidney injury (AKI) in
a patient subjected to a surgical procedure, comprising: a)
contacting, in vitro, a sample obtained from the patient after the
patient undergoes the surgical procedure with an antibody
immunoreactive for GDF-15; b) determining the amount of GDF-15 in
the sample; and c) providing a prediction that the patient is not
at risk of AKI if the amount of GDF-15 is below about 1807 pg/ml
and that the patient has an increased risk of AKI if the amount of
GDF-15 is above about 3389 pg/ml.
11. The method of claim 10, wherein the surgical procedure is
orthopedic surgery, a tumor resection, surgery of the
gastrointestinal tract not involving tumor resection, or cardiac
surgery.
12. The method of claim 10, wherein the sample is obtained from the
patient immediately after surgery or less than 1 day, 2 days, or 3
days after the patient undergoes the surgical procedure.
13. The method of claim 10, wherein the ligand comprising specific
binding affinity for GDF-15 is an antibody, nucleic acid, receptor,
binding partner, or aptamer.
14. The method of claim 10, wherein the amount of GDF-15 in the
sample is determined by measuring a signal obtained from GDF-15,
wherein the intensity of the signal directly correlates with the
number of molecules of GDF-15 in the sample.
15. The method of claim 10, wherein the amount of GDF-15 in the
sample is determined by measuring a signal obtained from a
secondary component, wherein the intensity of the signal indirectly
correlates with the number of molecules of GDF-15 in the
sample.
16. The method of claim 10, wherein the patient is predicted to
have an increased risk of AKI requiring hemodialysis if the amount
of GDF-15 is above about 6393 pg/ml.
17. The method of claim 10, further comprising contacting, in
vitro, the sample obtained from the patient after the patient
undergoes the surgical procedure with a second ligand comprising
specific binding affinity for troponin T; determining the amount of
troponin T in the sample; and providing a prediction that the
patient is not at risk of AKI if the amount of GDF-15 is below
about 1807 pg/ml and the amount of troponin T is below about 312.4
pg/ml, or that the patient has an increased risk of AKI if the
amount of GDF-15 is above about 3389 pg/ml and the amount of
troponin T is above about 503.6 pg/ml.
18. The method of claim 10, further comprising contacting, in
vitro, the sample obtained from the patient after the patient
undergoes the surgical procedure with a second ligand comprising
specific binding affinity for NT-proBNP; determining the amount of
NT-proBNP in the sample; and providing a prediction that the
patient is not at risk of AKI if the amount of GDF-15 is below
about 1807 pg/ml and the amount of NT-proBNP is below about 368.6
pg/ml, or that the patient has an increased risk of AKI if the
amount of GDF-15 is above about 3389 pg/ml and the amount of
NT-proBNP is above about 924.6 pg/ml.
19. The method of claim 10, further comprising contacting, in
vitro, the sample obtained from the patient after the patient
undergoes the surgical procedure with a second ligand comprising
specific binding affinity for troponin T and a third ligand
comprising specific binding affinity for NT-proBNP; determining the
amounts of troponin T and NT-proBNP in the sample; and providing a
prediction that the patient is not at risk of AKI if the amount of
GDF-15 is below about 1807 pg/ml, the amount of troponin T is below
about 312.4 pg/ml, and the amount of NT-proBNP is below about 368.6
pg/ml; or that the patient has an increased risk of AKI if the
amount of GDF-15 is above about 3389 pg/ml, the amount of troponin
T is above about 503.6 pg/ml, and the amount of NT-proBNP is above
about 924.6 pg/ml.
20. A device for predicting a risk of acute kidney injury (AKI) in
a patient subjected to a surgical procedure, comprising: a) an
analyzing unit comprising means for contacting, in vitro, a sample
obtained from the patient before or after the patient undergoes the
surgical procedure with a ligand comprising specific binding
affinity for GDF-15, and means for determining the amount of GDF-15
in the sample; and b) an evaluation unit comprising a computer for
comparing the determined amount of GDF-15 with a reference amount,
predicting the risk of AKI during or immediately after the surgical
procedure, and providing an output indicating the risk of AKI.
Description
PRIORITY CLAIM
[0001] This application is a continuation of International
Application No. PCT/EP2010/070058, filed Dec. 17, 2010, which
claims the benefit of European Patent Application No. 09179925.4,
filed Dec. 18, 2009, the disclosures of which are hereby
incorporated by reference in their entirety.
FIELD OF THE DISCLOSURE
[0002] The present disclosure relates to the field of laboratory
diagnostics.
BACKGROUND OF THE DISCLOSURE
[0003] GDF-15 is a member of the TGF beta family; it is synthesized
as a 40 kD propeptide and undergoes cleavage of its N-terminal
moiety to generate an active 30 kD disulfide-linked dimeric protein
that is secreted. GDF-15 has been linked to heart failure and to
cardiac reperfusion injury (Kempf et al., 2006, Cir. Res. 98(3):
351-60). GDF-15 has been shown to be induced in many tissues in
response to various stresses.
[0004] Troponin T is a part of the contractile apparatus of
cardiomyocytes. It is a well established biomarker of myocardial
necrosis or damage. In line with these findings, it has been shown
that elevated troponin T levels measured within 24 hours after
coronary artery bypass graft surgery indicate an increased risk of
postoperative complications (Mohammed et al., 2009, Circulation
120(10): 843-50).
[0005] Patients with advanced cardiovascular atherosclerosis
benefit from percutaneous cardiovascular intervention (PCI), as
summarized by the ACC/AHA guidelines for Revascularization with PCI
and coronary artery bypass graft surgery (CABG) in patients with
stable angina (Eagle et al., 2004,Circulation 110(14):
e340-437).
[0006] Coronary bypass surgery, however, is associated with a
significant risk of complications. For example, the incidence of
acute kidney injury (AKI) after coronary bypass surgery ranges from
10 to 20% (Mehta et al., 2006, Circulation 114(21): 2208-16). In
addition, 1% to 5% of individuals undergoing coronary bypass
surgery require postoperative dialysis. The pathogenesis of
postoperative AKI appears multifactorial and its association with
increased morbidity and long term mortality after cardiac surgery
is well established (Brown et al., 2008, Ann. Thorac. Surg. 86(1):
4-11).
[0007] AKI may be prevented in at-risk patients. Preventive
measures include careful fluid balance during and after surgery,
avoidance of low cardiopulmonary bypass (CPB) perfusion
temperatures, avoidance of nephrotoxic drugs prior to surgery, and
application of drugs such as erythropoietin after surgery (Song et
al., 2009, Am. J. Nephrol. 30(3): 253-60).
[0008] Therefore, it is of high importance to identify individuals
at risk of complications before cardiovascular surgery to avoid
risk factors that might lead to AKI. Moreover, in at-risk
individuals, careful follow up of kidney function after surgery is
indicated.
[0009] Consequently, the technical problem underlying the present
disclosure could be seen as the provision of means and methods for
identifying individuals that have an elevated risk of acute kidney
injury after a surgical procedure. The problem is solved by the
embodiments of the present disclosure described in the claims and
in the specification below.
SUMMARY OF THE DISCLOSURE
[0010] The present disclosure relates to the field of laboratory
diagnostics. Specifically, means and methods are disclosed for
determining the risk of acute kidney injury in a patient following
a surgical procedure by determining the amount of GDF-15, troponin,
and/or natriuretic peptide.
[0011] Thus, the present disclosure relates to a method for
predicting the risk of acute kidney injury (AKI) in an at-risk
patient subjected to a surgical procedure, comprising the steps of
determining the amount of GDF-15, troponin, and/or natriuretic
peptide in a sample obtained from the patient; and comparing the
amount of GDF-15, troponin T, and/or natriuretic peptide in the
sample with a suitable reference amount, whereby the risk of AKI in
the at-risk patient is predicted.
[0012] The present disclosure also relates to a method for
predicting the risk of AKI in an at-risk patient subjected to a
surgical procedure, comprising the step of comparing the amount of
GDF-15, troponin, and/or natriuretic peptide determined in a sample
obtained from the patient with a suitable reference amount, whereby
the risk of AKI is predicted.
[0013] The present disclosure further relates to in vitro methods
for predicting the risk of AKI in an at-risk patient subjected to a
surgical procedure based on the biomarker GDF-15, troponin, and/or
natriuretic peptide. Such methods may comprise steps in addition to
those described above, including steps for sample pre-treatment or
evaluation of results obtained by the method.
[0014] The methods of the present disclosure may be carried out
manually or may be automated. One or more steps of the disclosed
methods may be automated, e.g., by suitable robotic and sensory
equipment for determining the amount of GDF-15, troponin, and/or
natriuretic peptide in a patient sample, or by a
computer-implemented step of comparing the amount of GDF-15,
troponin, and/or natriuretic peptide determined in a sample from a
patient with a suitable reference amount.
[0015] The above-described embodiments of the various aspects of
the disclosure may be used alone or in any combination thereof
without departing from the scope of the disclosure.
DETAILED DESCRIPTION OF THE EMBODIMENTS OF THE DISCLOSURE
[0016] The embodiments disclosed herein are not intended to be
exhaustive or limit the disclosure to the precise form disclosed in
the following detailed description. Rather, the embodiments are
chosen and described so that others skilled in the art may utilize
their teachings.
[0017] The term "predicting the risk" as used herein refers to
assessing the probability that a subject will suffer from acute
kidney injury within a certain time window, i.e., the predictive
window. In accordance with the present disclosure, the predictive
window may be within 1 day, 2 days, or 3 days after completion of
the intervention. The endpoint of acute kidney injury within the
predictive window will become apparent by an increase of the serum
creatinine as described herein. However, as will be understood by
those skilled in the art, such an assessment is usually not
intended to be correct for 100% of the subjects to be investigated.
The term, however, requires that a prediction can be made for a
statistically significant portion of subjects in a proper and
correct manner. Whether a portion is statistically significant can
be determined by those skilled in the art using various well known
statistic evaluation tools, e.g., determination of confidence
intervals, p-value determination, Student's t-test, and
Mann-Whitney test. Details regarding suitable statistic evaluation
tools can be found in Dowdy and Wearden, Statistics for Research
(John Wiley & Sons, New York 1983). Suitable confidence
intervals are at least 90%, at least 95%, at least 97%, at least
98%, or at least 99%. Suitable p-values are 0.1, 0.05, 0.01, 0.005,
or 0.0001. In one embodiment of the disclosed methods, the
probability envisaged by the present disclosure allows that the
prediction of an increased, normal, or decreased risk will be
correct for at least 60%, at least 70%, at least 80%, or at least
90% of the subjects of a given cohort or population. Predictions of
risk in the disclosed methods relate to predicting whether or not
there is an increased risk for acute kidney injury compared to the
average risk for developing acute kidney injury in a population of
subjects rather than giving a precise probability for the risk.
[0018] An "at-risk patient" according to the present disclosure is
a patient who will suffer from acute kidney injury following a
surgical procedure, with a statistically significant increased
probability compared to the incidence of said acute kidney injury
in a population of individuals subjected to the intervention. In
one embodiment, the surgical procedure is a severe surgical
procedure. In another embodiment, the population of individuals
subjected to the intervention is a control population or a
randomized population. Pre-existing underlying disorders increase
the risk that the patient will suffer from acute kidney injury
following a surgical procedure. In one embodiment, the at-risk
patient is a patient suffering from a cardiovascular disease and/or
diabetes. In another embodiment, the patient suffers from
cardiovascular atherosclerosis that requires treatment by coronary
artery bypass surgery (CABP). In a patient suffering from
cardiovascular atherosclerosis accompanying diseases, such as
diabetes or cardiovascular disease, the risk of acute kidney injury
increases. In one embodiment, the cardiovascular atherosclerosis
accompanying disease is cardiovascular disease, and more
particularly, heart failure or hypertension. In another embodiment,
the cardiovascular atherosclerosis accompanying disease is
diabetes, and more particularly, type 1 or type 2 diabetes. In one
embodiment, the severity of the cardiovascular disease in patients
in need of CABG is higher than in patients in need of other types
of surgical procedures. In some embodiments, an increasing severity
of the cardiovascular disease increases the risk of acute kidney
injury after the surgical procedure. Except for the aforementioned
specific diseases or conditions, the at-risk patient may appear to
be apparently healthy.
[0019] The term "surgical procedure," as used herein, may refer to
any surgical procedure that requires general anaesthesia and
pulmonary or cardiopulmonary support. In some embodiments, the
surgical procedure, which may be severe, is characterized by a
duration of more than 30 minutes, or more than about 1, or more
than about 2 hours. In certain embodiments, the surgical procedure
is orthopedic surgery, a tumor resection, surgery of the
gastrointestinal tract not involving tumor resection (e.g., the
removal of diverticula), or cardiac surgery. In one embodiment, the
surgical procedure is cardiac surgery, and more particularly,
coronary artery bypass graft (CABG) surgery. CABG is indicated if a
patient suffers from stenosis of the coronary arteries which cannot
be treated successfully with other methods such percutaneous
coronary intervention (PCI). This is typically the case if multiple
vessels are affected or if the stenosis is not clearly localized.
CABG is either performed "on-pump," i.e., the heart is stopped and
does not beat during surgery, or "off-pump," i.e., the heart
continues to beat during the procedure.
[0020] The term "acute kidney injury" or "AKI" refers to an
impaired kidney function. AKI is characterized by an increase of
serum creatinine of at least 0.3 mg/dl within 72 hours after
surgery or by an increase of at least 50% from baseline. Typically,
not all cases of AKI lead to functional impairment of the kidneys,
which would require a renal replacement therapy. In severe cases of
acute kidney injury, renal replacement therapy by hemodialysis to
support the failing kidney function of the patient is required.
[0021] Acute kidney injury may occur during or immediately after
the surgical procedure. In one embodiment, AKI begins during the
surgical procedure or not later than 1, 2, or 3 days after surgery.
Depending on the diagnostic method applied, it may only be
recognizable several days after onset. In certain embodiments,
acute kidney injury is not only temporally but also causally
associated with the surgical procedure, i.e., the surgical
procedure or its surrounding circumstances are the reason why the
patient in question suffers from acute kidney injury.
[0022] The term "growth differentiation factor-15" or "GDF-15"
relates to a polypeptide that is a member of the transforming
growth factor (TGF)-.beta. cytokine superfamily. The terms
polypeptide, peptide, and protein are used interchangeably
throughout this specification. GDF-15 was originally cloned as
macrophage-inhibitory cytokine-1 and later also identified as
placental transforming growth factor-.beta., placental bone
morphogenetic protein, non-steroidal anti-inflammatory
drug-activated gene-1, and prostate-derived factor (Hromas et al.,
1997, Biochim. Biophys. Acta 1354(1): 40-44; Lawton et al., 1997,
Gene 203(1): 17-26; Yokoyama-Kobayashi et al., 1997, J. Biochem.
122(30: 622-26; Paralkar et al., 1998, J. Biol. Chem. 273(22):
13760-67). Similar to other TGF-.beta.-related cytokines, GDF-15 is
synthesized as an inactive precursor protein, which undergoes
disulfide-linked homodimerization. Upon proteolytic cleavage of the
N-terminal pro-peptide, GDF-15 is secreted as a .about.28 kD
dimeric protein (Bauskin et al., 2000, EMBO J. 19(10): 2212-20).
Amino acid sequences and biological activities for GDF-15 are
described in International Publication Nos. WO 99/06445, WO
00/70051, and WO 2005/113585; Bottner et al., 1999, Gene 237:
105-11; Baek et al., 2001, Mol. Pharmacol. 59(4): 901-08, Hromas et
al., 1997; Paralkar et al., 1998; Morrish et al., 1996, Placenta
17(7): 431-41; Yokoyama-Kobayashi et al., 1997.
[0023] The term "troponin" refers to all troponin isoforms
expressed in cells of the heart and subendocardial cells. These
isoforms are well characterized in the art as described in, for
example, Anderson et al., 1995, Circ. Res. 76(4): 681-86, and
Ferrieres et al., 1998, Clin. Chem. 44(3): 487-93. In the disclosed
methods, troponin may refer to troponin T and/or troponin I.
Accordingly, both troponins may be determined in the method of the
present disclosure together, i.e., simultaneously or sequentially,
or individually, i.e., without determining the other isoform at
all. Amino acid sequences for human troponin T and human troponin I
are described in Anderson et al., 1995 and Ferrieres et al., 1998.
The term "troponin" encompasses also variants of the aforementioned
specific troponins, i.e., troponin T or troponin I.
[0024] The terms "GDF-15," "natriuretic peptide," and "troponin,"
as used herein, also encompass variants of the aforementioned
specific polypeptides. Such variants have at least the same
essential biological and immunological properties as the specific
polypeptide of the present disclosure. In particular, they share
the same essential biological and immunological properties if they
are detectable by the same specific assays referred to in this
specification, e.g., by ELISA assays using polyclonal or monoclonal
antibodies specifically recognizing said polypeptides. Moreover, it
is to be understood that a variant as referred to in the present
disclosure shall have an amino acid sequence having at least one
amino acid substitution, deletion, and/or addition wherein the
amino acid sequence of the variant is still at least about 50%, at
least about 60%, at least about 70%, at least about 80%, at least
about 85%, at least about 90%, at least about 92%, at least about
95%, at least about 97%, at least about 98%, or at least about 99%
identical to the amino sequence of the polypeptide of the present
disclosure, over the entire length of the peptide. In the context
of sequence identity of amino acid sequences or nucleic acid
sequences, the term "at least about" refers to a sequence identity
exceeding the indicated exact numerical value. The degree of
identity between two amino acid sequences can be determined by
algorithms well known in the art. In certain embodiments, the
degree of identity is to be determined by comparing two optimally
aligned sequences over a comparison window, where the fragment of
amino acid sequence in the comparison window may comprise additions
or deletions (e.g., gaps or overhangs) as compared to the reference
sequence (which does not comprise additions or deletions) for
optimal alignment. The percentage is calculated by determining the
number of positions at which the identical amino acid residue
occurs in both sequences to yield the number of matched positions,
dividing the number of matched positions by the total number of
positions in the window of comparison, and multiplying the result
by 100 to yield the percentage of sequence identity. Optimal
alignment of sequences for comparison may be conducted by the local
homology algorithm of Smith and Waterman, 1981, Adv. Appl. Math. 2:
482-89, by the homology alignment algorithm of Needleman and
Wunsch, 1970, J. Mol. Biol. 48(3): 443-53, by the search for
similarity method of Pearson and Lipman, 1988, Proc. Natl. Acad.
Sci. U.S.A. 85(8): 2444-48, by computerized implementations of
these algorithms (GAP, BESTFIT, BLAST, PASTA, and TFASTA in the
Wisconsin Genetics Software Package, Genetics Computer Group (GCG),
Madison, Wis.), or by visual inspection. Given that two sequences
have been identified for comparison, GAP and BESTFIT may be
employed to determine their optimal alignment and, thus, the degree
of identity. In one embodiment, the default values of 5.00 for gap
weight and 0.30 for gap weight length are used. Variants referred
to above may be allelic variants or any other species-specific
homologs, paralogs, or orthologs. Moreover, the variants referred
to herein include fragments or subunits of the specific polypeptide
or the aforementioned types of variants as long as these fragments
have the essential immunological properties and/or biological
activities as referred to above. Such fragments may be, e.g.,
degradation products of the polypeptides of the present disclosure.
Also included are variants that differ due to posttranslational
modifications such as phosphorylation or myristylation.
[0025] Determining the amount of GDF-15, a natriuretic peptide,
troponin, or any other peptide or polypeptide referred to in this
specification relates to measuring the amount or concentration. In
certain embodiments, such measurements are semi-quantitative or
quantitative. Measuring can be done directly or indirectly. Direct
measuring relates to measuring the amount or concentration of the
peptide or polypeptide based on a signal which is obtained from the
peptide or polypeptide itself and the intensity of which directly
correlates with the number of molecules of the peptide present in
the sample. Such a signal--sometimes referred to herein as
intensity signal--may be obtained, for example, by measuring an
intensity value of a specific physical or chemical property of the
peptide or polypeptide. Indirect measuring includes measuring of a
signal obtained from a secondary component (i.e., a component not
being the peptide or polypeptide itself) or a biological read out
system, e.g., measurable cellular responses, ligands, labels, or
enzymatic reaction products.
[0026] In accordance with the present disclosure, determining the
amount of a peptide or polypeptide can be achieved by all known
means for determining the amount of a peptide in a sample. Said
means comprise immunoassay devices and methods that may utilize
labelled molecules in various sandwich, competition, or other assay
formats. Said assays will develop a signal which is indicative for
the presence or absence of the peptide or polypeptide. Moreover,
the signal strength can be correlated directly or indirectly (e.g.,
reverse-proportional) to the amount of polypeptide present in a
sample. Other suitable methods comprise measuring a physical or
chemical property specific for the peptide or polypeptide such as
its precise molecular mass or NMR spectrum. Said methods may
comprise biosensors, optical devices coupled to immunoassays,
biochips, and analytical devices such as mass-spectrometers,
NMR-analyzers, or chromatography devices. Other suitable methods
include micro-plate ELISA-based methods, fully-automated or robotic
immunoassays (available, for example, on ELECSYS.TM. analyzers),
CBA (an enzymatic Cobalt Binding Assay, available, for example, on
ROCHE-HITACHI.TM. analyzers), and latex agglutination assays
(available, for example, on ROCHE-HITACHI.TM. analyzers).
[0027] In one embodiment of the methods of the disclosure, the
amount of a peptide or polypeptide is determined by contacting a
cell capable of eliciting a cellular response, wherein the
intensity is indicative of the amount of the peptide or
polypeptide, with said peptide or polypeptide for an adequate
period of time, and measuring the cellular response. For measuring
cellular responses, the sample or processed sample can be added to
a cell culture and an internal or external cellular response is
measured. The cellular response may include the measurable
expression of a reporter gene or the secretion of a substance,
e.g., a peptide, polypeptide, or a small molecule. The expression
or substance shall generate an intensity signal that correlates to
the amount of the peptide or polypeptide.
[0028] In another embodiment of the methods of the disclosure, the
amount of a peptide or polypeptide is determined by measuring a
specific intensity signal obtainable from the peptide or
polypeptide in the sample. As described above, such a signal may be
the signal intensity observed at an m/z variable specific for the
peptide or polypeptide observed in mass spectra or a NMR spectrum
specific for the peptide or polypeptide.
[0029] In another embodiment of the methods of the disclosure, the
amount of a peptide or polypeptide is determined by contacting the
peptide with a specific ligand, optionally removing non-bound
ligand, and measuring the amount of bound ligand. The bound ligand
will generate an intensity signal. Binding according to the present
disclosure includes both covalent and non-covalent binding. A
ligand according to the present disclosure can be any compound,
e.g., a peptide, polypeptide, nucleic acid, or small molecule,
binding to the peptide or polypeptide described herein. Suitable
ligands include antibodies, nucleic acids, peptides or polypeptides
such as receptors or binding partners for the peptide or
polypeptide and fragments thereof comprising the binding domains
for the peptides, and aptamers, e.g., nucleic acid or peptide
aptamers. Methods to prepare such ligands are well known in the
art. For example, identification and production of suitable
antibodies or aptamers is offered by commercial suppliers. Those
skilled in the art are familiar with methods to develop derivatives
of such ligands with higher affinity or specificity. For example,
random mutations can be introduced into the nucleic acids,
peptides, or polypeptides. These derivatives can then be tested for
binding according to screening procedures known in the art, e.g.,
phage display. Antibodies as referred to herein include both
polyclonal and monoclonal antibodies, as well as fragments thereof,
such as Fv, Fab and F(ab).sub.2 fragments that are capable of
binding antigen or hapten. The present disclosure also includes
single chain antibodies and humanized hybrid antibodies wherein
amino acid sequences of a non-human donor antibody exhibiting a
desired antigen-specificity are combined with sequences of a human
acceptor antibody. The donor sequences will usually include at
least the antigen-binding amino acid residues of the donor but may
comprise other structurally and/or functionally relevant amino acid
residues of the donor antibody as well. Such hybrids can be
prepared by several methods well known in the art. In some
embodiments, the ligand or agent specifically binds to the peptide
or polypeptide. Specific binding according to the present
disclosure means that the ligand or agent should not bind
substantially to ("cross-react" with) another peptide, polypeptide,
or substance present in the sample to be analyzed. In certain
embodiments, the specifically bound peptide or polypeptide should
be bound with at least 3 times higher, at least 10 times higher, or
at least 50 times higher affinity than any other relevant peptide
or polypeptide. Non-specific binding may be tolerable if it can
still be distinguished and measured unequivocally, e.g., according
to its size on a Western Blot, or by its relatively higher
abundance in the sample. Binding of the ligand can be measured by
any method known in the art. In certain embodiments, the method is
semi-quantitative or quantitative. Suitable methods are described
herein.
[0030] First, binding of a ligand may be measured directly, e.g.,
by NMR or surface plasmon resonance.
[0031] Second, if the ligand also serves as a substrate of an
enzymatic activity of the peptide or polypeptide of interest, an
enzymatic reaction product may be measured (e.g., the amount of a
protease can be measured by measuring the amount of cleaved
substrate, e.g., on a Western Blot). Alternatively, the ligand may
exhibit enzymatic properties itself and the "ligand/peptide or
polypeptide" complex or the ligand which was bound by the peptide
or polypeptide, respectively, may be contacted with a suitable
substrate allowing detection by the generation of an intensity
signal. For measurement of enzymatic reaction products, the amount
of substrate can be saturating. The substrate may also be labelled
with a detectable label prior to the reaction. In one embodiment,
the sample is contacted with the substrate for an adequate period
of time. An adequate period of time refers to the time necessary
for a detectable and measurable amount of product to be produced.
Instead of measuring the amount of product, the time necessary for
appearance of a given (e.g., detectable) amount of product can be
measured.
[0032] Third, the ligand may be coupled covalently or
non-covalently to a label allowing detection and measurement of the
ligand. Labelling may be done by direct or indirect methods. Direct
labelling involves coupling of the label directly (covalently or
non-covalently) to the ligand. Indirect labelling involves binding
(covalently or non-covalently) of a secondary ligand to the first
ligand. The secondary ligand should specifically bind to the first
ligand. Said secondary ligand may be coupled with a suitable label
and/or be the target (receptor) of tertiary ligand binding to the
secondary ligand. Secondary, tertiary, or even higher order ligands
are often used to increase the signal. Suitable secondary and
higher order ligands may include antibodies, secondary antibodies,
and the well-known streptavidin-biotin system (Vector Laboratories,
Inc.). The ligand or substrate may also be "tagged" with one or
more tags as known in the art. Such tags may then be targets for
higher order ligands. Suitable tags include biotin, digoxygenin,
His-Tag, Glutathione-S-transferase, FLAG, GFP, myc-tag, influenza A
virus hemagglutinin (HA), maltose binding protein, and the like. In
the case of a peptide or polypeptide, the tag may be located at the
N-terminus and/or C-terminus. Suitable labels are any labels
detectable by an appropriate detection method. Typical labels
include gold particles, latex beads, acridan ester, luminol,
ruthenium, enzymatically active labels, radioactive labels,
magnetic labels (e.g., magnetic beads, including paramagnetic and
superparamagnetic labels), and fluorescent labels. Enzymatically
active labels include e.g., horseradish peroxidase, alkaline
phosphatase, beta-Galactosidase, Luciferase, and derivatives
thereof. Suitable substrates for detection include
di-amino-benzidine (DAB), 3,3'-5,5'-tetramethylbenzidine, NBT-BCIP
(4-nitro blue tetrazolium chloride and
5-bromo-4-chloro-3-indolyl-phosphate, available as ready-made stock
solution from Roche Diagnostics), CDP-STAR.TM. (Amersham
Biosciences), ECF.TM. (Amersham Biosciences). A suitable
enzyme-substrate combination may result in a colored reaction
product, fluorescence, or chemoluminescence, which can be measured
according to methods known in the art (e.g., using a
light-sensitive film or a suitable camera system). As for measuring
the enzymatic reaction, the criteria given above apply analogously.
Typical fluorescent labels include fluorescent proteins (such as
GFP and its derivatives), Cy3, Cy5, Texas Red, Fluorescein, and the
Alexa dyes (e.g., Alexa 568). Other fluorescent labels are
available e.g., from Molecular Probes (Oregon). Also the use of
quantum dots as fluorescent labels is contemplated. Typical
radioactive labels include .sup.35S, .sup.125I, .sup.32P, .sup.33P,
and the like. A radioactive label can be detected by any method
known and appropriate, e.g., a light-sensitive film or a phosphor
imager. Suitable measurement methods according the present
disclosure also include precipitation (particularly
immunoprecipitation), electrochemiluminescence (electro-generated
chemiluminescence), RIA (radioimmunoassay), ELISA (enzyme-linked
immunosorbent assay), sandwich enzyme immune tests,
electrochemiluminescence sandwich immunoassays (ECLIA),
dissociation-enhanced lanthanide fluoro immuno assay (DELFIA),
scintillation proximity assay (SPA), turbidimetry, nephelometry,
latex-enhanced turbidimetry or nephelometry, or solid phase immune
tests. Other methods known in the art (such as gel electrophoresis,
2D gel electrophoresis, SDS polyacrylamide gel electrophoresis
(SDS-PAGE), Western Blotting, and mass spectrometry) can be used
alone or in combination with labelling or other detection methods
as described above.
[0033] The amount of a peptide or polypeptide may also be
determined by contacting a solid support comprising a ligand for
the peptide or polypeptide as specified above with a sample
comprising the peptide or polypeptide and measuring the amount
peptide or polypeptide which is bound to the support. The ligand
may be chosen from the group consisting of nucleic acids, peptides,
polypeptides, antibodies and aptamers, and can be present on a
solid support in immobilized form. Materials for manufacturing
solid supports are well known in the art and include, inter alia,
commercially available column materials, polystyrene beads, latex
beads, magnetic beads, colloid metal particles, glass and/or
silicon chips and surfaces, nitrocellulose strips, membranes,
sheets, duracytes, wells and walls of reaction trays, and plastic
tubes. The ligand or agent may be bound to many different carriers.
Examples of well-known carriers include glass, polystyrene,
polyvinyl chloride, polypropylene, polyethylene, polycarbonate,
dextran, nylon, amyloses, natural and modified celluloses,
polyacrylamides, agaroses, and magnetite. The nature of the carrier
can be either soluble or insoluble for the purposes of the
disclosure. Suitable methods for fixing/immobilizing said ligand
are well known and include, but are not limited to ionic,
hydrophobic, covalent interactions and the like. It is also
contemplated to use "suspension arrays" as arrays according to the
present disclosure (Nolan et al., 2002, Trends Biotechnol. 20(1):
9-12). In such suspension arrays, the carrier, e.g., a microbead or
microsphere, is present in suspension. The array consists of
different microbeads or microspheres, possibly labelled, carrying
different ligands. Methods of producing such arrays, for example
based on solid-phase chemistry and photo-labile protective groups,
are generally known (U.S. Pat. No. 5,744,305).
[0034] The term "sample" refers to a sample of a body fluid, to a
sample of separated cells or to a sample from a tissue or an organ.
Samples of body fluids can be obtained by well known techniques and
include, for example, samples of blood, plasma, serum, or urine. In
certain embodiments of the disclosed methods, the sample is blood,
plasma, or serum. Tissue or organ samples may be obtained from any
tissue or organ by, e.g., biopsy. Separated cells may be obtained
from the body fluids or the tissues or organs by separating
techniques such as centrifugation or cell sorting. In some
embodiments, cell, tissue, or organ samples are obtained from those
cells, tissues, or organs that express or produce the peptides
referred to herein. In one embodiment, the sample has been taken
before the patient undergoes the surgical procedure, and in
particular, the sample has been taken within 1 day before to 6
weeks before the surgical procedure is carried out. In certain
embodiments, the sample is taken 1 or 2 days before the surgical
procedure. In a stable patient, i.e., in a patient whose health
status does not change, it may be desired to take the sample within
1 or 2 weeks before the surgical procedure. In an unstable patient
the sample may be taken within 6 hours, 12 hours, or 24 hours
before the surgical procedure.
[0035] The term "comparing" as used herein encompasses comparing
the amount of the peptide or polypeptide comprised by the sample to
be analyzed with an amount of a suitable reference source specified
elsewhere in this description. It is to be understood that
comparing as used herein refers to a comparison of corresponding
parameters or values, e.g., an absolute amount is compared to an
absolute reference amount while a concentration is compared to a
reference concentration or an intensity signal obtained from a test
sample is compared to the same type of intensity signal of a
reference sample. A comparison may be carried out manually or with
the assistance of a computer. For a computer assisted comparison,
the value of the determined amount may be compared to values
corresponding to suitable references which are stored in a database
by a computer program. The computer program may further evaluate
the result of the comparison, i.e., automatically provide the
desired assessment in a suitable output format. Based on the
comparison of the amounts determined in step a) and the reference
amount of the method of the present disclosure, it is possible to
predict the risk of the patient suffering from one or more of the
complications referred to herein. Therefore, the reference amount
is to be chosen so that either a difference or a similarity in the
compared amounts allows identifying those patients who are at risk
of acute kidney injury after a surgical procedure.
[0036] Accordingly, the term "reference amount" as used herein
refers to an amount which allows predicting whether a patient has
an increased risk of acute kidney injury after a surgical
procedure. Accordingly, the reference may either be derived from
(i) a sample taken from a patient before being subjected to a
surgery and known to have suffered from acute kidney injury
afterwards or (ii) a sample taken from a patient before being
subjected to a surgery and known to have not suffered from acute
kidney injury after surgery. In one embodiment, the reference
amount is determined on the basis of an averaged median amount
obtained from a group of patients meeting the criteria either of
(i) or of (ii), described above. Moreover, the reference amount may
define a threshold amount, whereby an amount larger than the
threshold shall be indicative for a subject that is at increased
risk of AKI. The reference amount applicable for an individual
subject may vary depending on various physiological parameters such
as age, gender, or subpopulation, as well as on the means used for
the determination of the polypeptide or peptide referred to herein.
A suitable reference amount may be determined by the method of the
present disclosure from a reference sample to be analyzed together,
i.e., simultaneously or subsequently, with the test sample. In
certain embodiments, the reference amount serving as a threshold
may be derived from the upper limit of normal (ULN), i.e., the
upper limit of the physiological amount to be found in samples from
a population of subjects before being subjected to a surgery and
who have not suffered or are not suffering from the complications
as defined above, i.e., subjects known to have not suffered from
acute kidney injury after surgery. The ULN for a given population
of subjects can be determined by various well-known techniques. A
suitable technique may be to determine the median or average of the
population for the peptide or polypeptide amounts to be determined
in the method of the present disclosure.
[0037] Reference amounts of a diagnostic marker (i.e., of GDF-15, a
natriuretic peptide or troponin) can be established, and the level
of the marker in a patient sample can simply be compared to the
reference amount. The sensitivity and specificity of a diagnostic
and/or prognostic test depends on more than just the analytical
"quality" of the test--they also depend on the definition of what
constitutes an abnormal result. In one embodiment, the distribution
of the measured amounts of the markers of the present disclosure in
a population of patients having suffered from acute kidney injury
after a surgical procedure are compared to the distribution of the
amounts of said marker in patients without said complications. In
another embodiment, the distribution is determined in samples taken
prior to surgery. Statistical methods well known to the person
skilled in the art can be used to define a threshold amount that
can be used to separate patients at risk of suffering from said
complications and patients not at risk. A suitable statistical
method for this purpose is the calculation of Receiver Operating
Characteristic curves, or "ROC" curves. ROC-curves are typically
calculated by plotting the value of a variable versus its relative
frequency in "normal" and "disease" populations. For any particular
marker, a distribution of marker levels for subjects with and
without a disease will likely overlap. Under such conditions, a
test does not absolutely distinguish normal from disease with 100%
accuracy, and the area of overlap indicates where the test cannot
distinguish normal from disease. A threshold may be selected above
which (or below which, depending on how a marker changes with the
disease) the test is considered to be abnormal and below which the
test is considered to be normal. The area under the ROC curve is a
measure of the probability that the perceived measurement will
allow correct identification of a condition. ROC curves can be used
even when test results do not necessarily give an accurate number.
As long as one can rank results, one can create an ROC curve. For
example, results of a test on "disease" samples might be ranked
according to degree (say 1=low, 2=normal, and 3=high). This ranking
can be correlated to results in the "normal" population, and a ROC
curve created. These methods are well known in the art. See, e.g.,
Hanley et al., 1982, Radiology 143(1): 29-36.
[0038] In certain embodiments, markers (i.e., GDF-15, a natriuretic
peptide or troponin) are selected to exhibit at least about 70%
sensitivity, or at least about 80% sensitivity, or at least about
85% sensitivity, or at least about 90% sensitivity, or at least
about 95% sensitivity, combined with at least about 70%
specificity, or at least about 80% specificity, or at least about
85% specificity, or at least about 90% specificity, or at least
about 95% specificity. In certain embodiments, both the sensitivity
and specificity are at least about 75%, or at least about 80%, or
at least about 85%, or at least about 90%, or at least about
95%.
[0039] In some embodiments of the disclosed methods, a pre-surgical
amount of GDF-15 below about 1078 pg/ml rules out the risk of AKI
after surgery, and a pre-surgical amount of GDF-15 above about 1717
pg/ml indicates an increased risk of AKI after surgery. In other
embodiments, a pre-surgical amount of GDF-15 above about 2573 pg/ml
indicates an increased risk of acute kidney injury requiring
hemodialysis. Suitable threshold values of GDF-15 indicating a risk
of AKI or AKI requiring hemodialysis based on the 75th percentiles,
or for ruling out a risk of AKI or AKI requiring hemodialysis based
on the 25th percentiles, are recited in Table 1 a.
[0040] In some embodiments of the disclosed methods, a pre-surgical
amount of troponin below about 7.7 pg/ml or about 13.3 pg/ml rules
out the risk of AKI after surgery, and a pre-surgical amount of
troponin above about 25.5 pg/ml or about 33.1 pg/ml indicates an
increased risk of AKI after surgery. In other embodiments, a
pre-surgical amount of troponin above about 60.9 pg/ml indicates an
increased risk of acute kidney injury requiring hemodialysis.
Suitable threshold values of troponin indicating a risk of AKI or
AKI requiring hemodialysis based on the 75th percentiles, or for
ruling out a risk of AKI or AKI requiring hemodialysis based on the
25th percentiles, are recited in Table 1 b.
[0041] In some embodiments of the disclosed methods, a pre-surgical
amount of NT-proBNP below about 160.3 pg/ml or about 488.2 pg/ml
rules out the risk of AKI after surgery, and a pre-surgical amount
of NT-proBNP above about 1118.7 pg/ml or about 1385.5 pg/ml
indicates an increased risk of AKI after surgery. In some
embodiments, a pre-surgical amount of NT-proBNP above about 2227.1
pg/ml indicates an increased risk of acute kidney injury requiring
hemodialysis. Suitable threshold values of NT-proBNP indicating a
risk of AKI or AKI requiring hemodialysis based on the 75th
percentiles, or for ruling out a risk of AKI or AKI requiring
hemodialysis based on the 25th percentiles, are recited in Table
1c.
[0042] The term "about" is meant to indicate +/-30% of the
indicated amount, or +/-20% of the indicated amount, or +/-10% of
the indicated amount, or +/-5% of the indicated amount.
[0043] As set forth above, the reference amount may also be derived
from a sample taken from a patient before being subjected to a
surgery and known to have suffered from acute kidney injury
afterwards. In some embodiments, an essentially identical or
increased amount with respect to said reference amount of the
biomarker GDF15, troponin and/or troponin indicates an increased
risk of acute kidney injury after surgery. As set forth above, the
reference amount may also be derived from a sample taken from a
patient before being subjected to a surgery and known to have
suffered from acute kidney injury and requiring hemodialysis
afterwards. In some embodiments, an essentially identical or
increased amount with respect to said reference amount of the
biomarker GDF15 and/or troponin indicates an increased risk of AKI
requiring hemodialysis after surgery.
[0044] Moreover, the reference amount may be obtained from a sample
taken from a patient before being subjected to a surgery and known
to have not suffered from acute kidney injury after surgery. In
some embodiments, an essentially identical or decreased amount with
respect to said reference amount of the biomarker GDF15 and/or
troponin rules out the risk of AKI after surgery (and, thus,
indicates that the risk is low).
[0045] Advantageously, the method of the present disclosure allows
for the identification of patients with an increased risk of AKI
prior to the surgical procedure. This is based on the surprising
finding that the amounts of the markers of the present disclosure
determined in a patient prior to the surgical procedure predict the
risk of the patient suffering from acute kidney injury after the
surgical procedure. From the determination of an increased risk of
AKI in a patient practical consequences can be drawn immediately:
known risk factors that precipitate AKI have to be controlled in a
patient having an increased risk of acute kidney injury after a
surgical procedure. Control of these risk factors includes careful
fluid balance during and after surgery. If a cardiopulmonary bypass
is used during surgery, low perfusion temperatures have to be
avoided (Kourliouros et al., 2009). Nephrotoxic drugs (e.g., non
steroidal anti-inflammatory drugs and sulfonamides) have to be
avoided as well. Moreover, the administration of erythropoietin may
be indicated (Song et al., 2009). The possibility to predict the
risk of acute kidney injury after a surgical procedure in a patient
prior to said intervention obviously has consequences for deciding
whether the patient in question is eligible for the surgical
procedure in question.
[0046] It will be understood that in another aspect of the method
of the present disclosure, said method is a method for predicting
in an at-risk patient who will be subjected to a surgical procedure
the risk suffering from acute kidney injury comprising the step of
comparing the amount of GDF-15 and/or troponin determined in a
sample of the patient with a suitable reference amount as described
herein to predict the risk of the patient suffering from acute
kidney injury.
[0047] In one embodiment of the present disclosure the amount of a
natriuretic peptide is determined in addition to the amount of
GDF-15 and/or troponin.
[0048] The term "natriuretic peptide" comprises Atrial Natriuretic
Peptide (ANP)-type and Brain Natriuretic Peptide (BNP)-type
peptides and variants thereof having the same predictive potential.
Natriuretic peptides according to the present disclosure comprise
ANP-type and BNP-type peptides and variants thereof (see, e.g.,
Bonow, 1996, Circulation 93(11): 1946-50). ANP-type peptides
comprise pre-proANP, proANP, NT-proANP, and ANP. BNP-type peptides
comprise pre-proBNP, proBNP, NT-proBNP, and BNP. The pre-pro
peptide (134 amino acids in the case of pre-proBNP) comprises a
short signal peptide, which is enzymatically cleaved off to release
the pro peptide (108 amino acids in the case of proBNP). The pro
peptide is further cleaved into an N-terminal pro peptide (NT-pro
peptide, 76 amino acids in case of NT-proBNP) and the active
hormone (32 amino acids in the case of BNP, 28 amino acids in the
case of ANP). Suitable natriuretic peptides for use in the
disclosed methods are NT-proANP, ANP, NT-proBNP, BNP, and variants
thereof. ANP and BNP are the active hormones and have a shorter
half-life than their respective inactive counterparts, NT-proANP
and NT-proBNP. BNP is metabolised in the blood, whereas NT-proBNP
circulates in the blood as an intact molecule and as such is
eliminated renally. The in vivo half-life of NTproBNP is 120 min
longer than that of BNP, which is 20 min. (Smith et al., 2000, J.
Endocrinol. 167(2): 239-46). Preanalytics are more robust with
NT-proBNP allowing easy transportation of the sample to a central
laboratory (Mueller et al., 2004, Clin. Chem. Lab. Med. 42(8):
942-44). Blood samples can be stored at room temperature for
several days or may be mailed or shipped without recovery loss. In
contrast, storage of BNP for 48 hours at room temperature or at
4.degree. Celsius leads to a concentration loss of at least 20%
(Mueller et al., 2004; Wu et al., 2004, Clin. Chem. 50(5): 867-73).
Therefore, depending on the time-course or properties of interest,
either measurement of the active or the inactive forms of the
natriuretic peptide can be advantageous. In certain embodiments,
the natriuretic peptides are NT-proBNP or variants thereof. As
briefly discussed above, the human NT-proBNP as referred to in the
present disclosure is a polypeptide comprising 76 amino acids in
length corresponding to the N-terminal portion of the human
NT-proBNP molecule. The structure of the human BNP and NT-proBNP
has been described already in detail in, e.g., International
Publication Nos. WO 02/089657 and WO 02/083913; and Bonow 1996. In
some embodiments, human NT-proBNP as used herein is human NT-proBNP
as disclosed in European Patent No. EP 0 648 228 B1. These prior
art documents are herewith incorporated by reference with respect
to the specific sequences of NT-proBNP and variants thereof
disclosed therein.
[0049] Moreover, it has been found in accordance with the present
disclosure that the amount of GDF-15 after the surgical procedure
is also indicative for an increased risk of acute kidney
injury.
[0050] Therefore, the present disclosure contemplates also a method
for predicting in an at-risk patient having been subjected to a
surgical procedure the risk of acute kidney injury comprising the
steps of determining the amount of GDF-15 in a sample of the
patient; and comparing the determined amount with a reference
amount, whereby the risk of acute kidney injury is predicted.
[0051] The explanations and definitions of the terms made above
apply mutatis mutandis. It will be understood that for the
disclosed methods, the sample has been taken after the surgical
procedure has been completed, and in some embodiments, within a
time window of not later than 1, 2, or 3 days after surgery. In
other embodiments, the sample is taken immediately or not later
than 1 day after completion of the intervention. In one such
embodiment, the sample is taken immediately after surgery, wherein
the term "immediately after surgery" refers to taking the sample
not later than about 0.5 hours, not later than about 1 hour, not
later than about 2 hours, not later than about 3 hours, or not
later than about 6 hours after surgery. In one such embodiment, the
sample is taken not later than 0.5 hours after surgery. The
disclosed methods can be practiced after surgery to diagnose as
early as possible, whether a patient having undergone a surgical
procedure has an increased risk of acute kidney injury. In order to
counter this risk effectively, therapeutic measures have to be
taken as early as possible.
[0052] In one embodiment of the disclosed methods, the risk of AKI
can be ruled out when the amount of GDF-15 in a sample taken
immediately after surgery is below about 1807 pg/ml. In another
embodiment, an amount of GDF-15 above about 3389 pg/ml indicates an
increased risk of AKI after surgery. In still another embodiment,
an amount of GDF-15 above about 6393 pg/ml indicates an increased
risk of acute kidney injury requiring hemodialysis.
[0053] In one embodiment of the disclosed methods, the risk of AKI
can be ruled out when the amount of GDF-15 in a sample taken 1 day
after surgery is below about 6375 pg/ml. In another embodiment, an
amount of GDF-15 above about 11988 pg/ml indicates an increased
risk of AKI after surgery. In still another embodiment, an amount
of GDF-15 above about 14507 pg/ml indicates, an increased risk of
acute kidney injury requiring hemodialysis. Suitable threshold
values of GDF-15 indicating a risk of AKI or AKI requiring
hemodialysis based on the 75th percentiles, or for ruling out a
risk of AKI or AKI requiring hemodialysis based on the 25th
percentiles, are recited in Table 2a.
[0054] In one embodiment of the disclosed methods, the risk of AKI
can be ruled out when the amount of GDF-15 in a sample taken 2 days
after surgery is below about 2352 pg/ml. In another embodiment, an
amount of GDF-15 above about 8034 pg/ml indicates an increased risk
of AKI after surgery. In still another embodiment, an amount of
GDF-15 above about 8929 pg/ml indicates, an increased risk of acute
kidney injury requiring hemodialysis. Suitable threshold values of
GFD-15 indicating a risk of AKI or AKI requiring hemodialysis based
on the 75th percentiles, or for ruling out a risk of AKI or AKI
requiring hemodialysis based on the 25th percentiles, are recited
in Table 2a.
[0055] In one embodiment of the disclosed methods, the risk of AKI
can be ruled out when the amount of GDF-15 in a sample taken 3 days
after surgery is below about 1903 pg/ml. In another embodiment, an
amount of GDF-15 above about 4675 pg/ml indicates an increased risk
of AKI after surgery. In still another embodiment, an amount of
GDF-15 above about 5938 pg/ml indicates an increased risk of acute
kidney injury requiring hemodialysis. Suitable threshold values
indicating a risk of AKI or AKI requiring hemodialysis based on the
75th percentiles, or for ruling out a risk of AKI or AKI requiring
hemodialysis based on the 25th percentiles, are recited in Table
2a.
[0056] In some embodiments of the disclosed methods, the risk of
AKI can be ruled out when the amount of troponin in a sample taken
immediately after surgery is below about 176.6 pg/ml or about 312.4
pg/ml. In other embodiments, an amount of troponin above about
503.6 pg/ml or about 593.1 pg/ml indicates an increased risk of AKI
after surgery. In still other embodiments, an amount of troponin
above about 640.3 pg/ml indicates an increased risk of acute kidney
injury requiring hemodialysis. Suitable threshold values indicating
a risk of AKI or AKI requiring hemodialysis based on the 75th
percentiles, or for ruling out a risk of AKI or AKI requiring
hemodialysis based on the 25th percentiles, are recited in Table
2b.
[0057] In some embodiments of the disclosed methods, the risk of
AKI can be ruled out when the amount of troponin in a sample taken
1 day after surgery is below about 364.5 pg/ml or about 863.9
pg/ml. In other embodiments, an amount of troponin above about
1108.1 pg/ml or about 1217.3 pg/ml indicates an increased risk of
AKI after surgery. In still other embodiments, an amount of
troponin above about 1280.9 pg/ml indicates an increased risk of
acute kidney injury requiring hemodialysis. Suitable threshold
values indicating a risk of AKI or AKI requiring hemodialysis based
on the 75th percentiles, or for ruling out a risk of AKI or AKI
requiring hemodialysis based on the 25th percentiles, are recited
in Table 2b.
[0058] In some embodiments of the disclosed methods, the risk of
AKI can be ruled out when the amount of troponin In a sample taken
2 days after surgery is below about 279.5 pg/ml or about 537.6
pg/ml. In other embodiments, an amount of troponin above about
739.1 pg/ml or about 856.0 pg/ml indicates an increased risk of AKI
after surgery. In still other embodiments, an amount of troponin
above about 981.3 pg/ml or about 2006.1 pg/ml indicates an
increased risk of acute kidney injury requiring hemodialysis.
Suitable threshold values indicating a risk of AKI or AKI requiring
hemodialysis based on the 75th percentiles, or for ruling out a
risk of AKI or AKI requiring hemodialysis based on the 25th
percentiles, are recited in Table 2b.
[0059] In some embodiments of the disclosed methods, the risk of
AKI can be ruled out when the amount of troponin in a sample taken
3 days after surgery is below about 182.7 pg/ml or about 370.9
pg/ml. In other embodiments, an amount of troponin above about
492.6 pg/ml or about 812.5 pg/ml indicates an increased risk of AKI
after surgery. In still other embodiments, an amount of troponin
above about 575.0 pg/ml or about 1424.2 pg/ml indicates an
increased risk of acute kidney injury requiring hemodialysis.
Suitable threshold values indicating a risk of AKI or AKI requiring
hemodialysis based on the 75th percentiles, or for ruling out a
risk of AKI or AKI requiring hemodialysis based on the 25th
percentiles, are recited in Table 2b.
[0060] In some embodiments of the disclosed methods, the risk of
AKI can be ruled out when the amount of NT-proBNP in a sample taken
immediately after surgery is below about 139.2 pg/ml or about 368.6
pg/ml. In other embodiments, an amount of NT-proBNP above about
924.6 pg/ml or about 940.3 pg/ml indicates an increased risk of AKI
after surgery. In still other embodiments, an amount of NT-proBNP
above about 1933.3 pg/ml indicates an increased risk of acute
kidney injury requiring hemodialysis. Suitable threshold values
indicating a risk of AKI or AKI requiring hemodialysis based on the
75th percentiles, or for ruling out a risk of AKI or AKI requiring
hemodialysis based on the 25th percentiles, are recited in Table
2c.
[0061] In some embodiments of the disclosed methods, the risk of
AKI can be ruled out when the amount of NT-proBNP in a sample taken
1 day after surgery is below about 914.1 pg/ml or about 1560.7
pg/ml. In other embodiments, an amount of NT-proBNP above about
1972.2 pg/ml or about 2565.1 pg/ml indicates an increased risk of
AKI after surgery. In still other embodiments, an amount of
NT-proBNP above about 3296.2 pg/ml or about 4876.7 pg/ml indicates,
an increased risk of acute kidney injury requiring hemodialysis.
Suitable threshold values indicating a risk of AKI or AKI requiring
hemodialysis based on the 75th percentiles, or for ruling out a
risk of AKI or AKI requiring hemodialysis based on the 25th
percentiles, are recited in Table 2c.
[0062] In some embodiments of the disclosed methods, the risk of
AKI can be ruled out when the amount of NT-proBNP in a sample taken
2 days after surgery is below about 1667.0 pg/ml or about 2717.2
pg/ml. In other embodiments, an amount of NT-proBNP above about
4618.5 pg/ml or about 4953.2 pg/ml indicates an increased risk of
AKI after surgery. In still other embodiments, an amount of
NT-proBNP above about 6597.7 pg/ml indicates, an increased risk of
acute kidney injury requiring hemodialysis. Suitable threshold
values indicating a risk of AKI or AKI requiring hemodialysis based
on the 75th percentiles, or for ruling out a risk of AKI or AKI
requiring hemodialysis based on the 25th percentiles, are recited
in Table 2c.
[0063] In some embodiments of the disclosed methods, the risk of
AKI can be ruled out when the amount of NT-proBNP in a sample taken
3 days after surgery is below about 1812.3 pg/ml or about 2825.0
pg/ml. In other embodiments, an amount of NT-proBNP above about
4983.7 pg/ml or about 5393.4 pg/ml indicates an increased risk of
AKI after surgery. In still other embodiments, an amount of
NT-proBNP above about 5291.9 pg/ml indicates an increased risk of
acute kidney injury requiring hemodialysis. Suitable threshold
values indicating a risk of AKI or AKI requiring hemodialysis based
on the 75th percentiles, or for ruling out a risk of AKI or AKI
requiring hemodialysis based on the 25th percentiles, are recited
in Table 2c.
[0064] The disclosed methods can also be applied for predicting
whether a patient is in need of renal replacement therapy including
hemodialysis, or for predicting a patient's mortality risk, or in
certain embodiments, for predicting an increased mortality risk for
a patient.
[0065] In one embodiment of the disclosed methods, the risk of
acute kidney injury in an at-risk patient who has been subjected to
a surgical procedure is predicted by comparing the amount of GDF-15
determined in a sample obtained from the patient with a suitable
reference amount as described herein to predict the risk of acute
kidney injury.
[0066] In other embodiments of the disclosed methods, the amount of
a natriuretic peptide and/or troponin is determined in addition to
the amount of GDF-15.
[0067] The present disclosure also relates to a method for
facilitating a surgical decision in an at-risk patient, comprising
the steps of determining the amount of GDF-15 and/or troponin in a
sample obtained from the patient; and comparing the amount GDF-15
and/or troponin in the sample with a suitable reference amount,
wherein the amount of GDF-15 and/or troponin in the sample
indicates whether the patient should undergo the surgical
procedure.
[0068] For each individual patient, the potential benefits of a
surgical procedure have to be balanced against the potential side
effects of that procedure. One potential side effect is acute
kidney injury. Because the disclosed methods allow for a risk
prediction on an individual basis, the decision about whether a
patient should undergo a surgical procedure can be made based on
the specific needs and risks of the patient. Accordingly, the
phrase "facilitating a surgical decision in an at-risk patient,"
means to make a risk stratification as described above, to balance
the risk and the benefit of the surgical procedure and to assist in
providing a recommendation for carrying out the procedure.
[0069] In one embodiment of the disclosed methods, the surgical
procedure is coronary artery bypass graft surgery. While CABG
improves the quality of life of patients, it does not lead to
prolonged survival (Eagle et al., 1999, J. Am. Coll. Cardiol.
34(4): 1262-347). Thus, in the case of planned CABG, the
potentially lethal consequences of AKI have to be balanced against
the potentially improved quality of life after CABG.
[0070] Some patients who are at risk of AKI following surgery are
not ideal candidates for a surgical procedure. In such patients,
the decision about performing the surgical procedure can be based
on the reference amounts of GDF-15 and/or troponin described
herein.
[0071] In one embodiment of the disclosed methods, a surgical
decision in an at-risk patient is facilitated by comparing the
amount of GDF-15 and/or troponin in a sample obtained from the
patient with a suitable reference amount as described herein, to
facilitate the surgical decision.
[0072] In one embodiment of the disclosed methods, the amount of a
natriuretic peptide is determined in addition to the amount of
GDF-15 and/or troponin.
[0073] The present disclosure also relates to the use of the
biomarker GDF15 and/or troponin in a sample of a patient who will
be subjected to a surgical procedure for predicting the risk of
acute kidney injury.
[0074] Moreover, the present disclosure relates to the use of a
detection agent that specifically binds to GDF15 and/or of a
detection agent that specifically binds to troponin in a sample of
a patient who will be subjected to a surgical procedure for
predicting the risk of acute kidney injury.
[0075] Also, the present disclosure relates to the use of the
biomarker GDF15 and/or a troponin in a sample of an at-risk patient
for deciding whether said patient is eligible for a surgical
procedure.
[0076] Moreover, the present disclosure relates to the use of a
detection agent that specifically binds to GDF15 and/or a detection
agent that specifically binds to troponin in a sample obtained from
an at-risk patient for deciding whether the patient should undergo
a surgical procedure.
[0077] Moreover, the present disclosure relates to the use of a
detection agent that specifically binds GDF15 in a sample obtained
from an at-risk patient having been subjected to a surgical
procedure for predicting the risk of acute kidney injury.
[0078] The term "detection agent," as used herein, refers to an
agent which is capable of specifically recognizing and binding to
one of the biomarkers referred to herein when present in a sample.
Moreover, the detection agent shall allow for direct or indirect
detection of the complex formed by the detection agent and the
biomarker. Direct detection can be achieved by incorporating a
detectable label in the detection agent. Indirect labelling may be
achieved by using a second agent that specifically binds to a
complex comprising the biomarker and the detection agent, wherein
the second agent is than capable of generating a detectable signal.
Suitable compounds for use as detection agents are well known in
the art. In some embodiments of the disclosed methods, the
detection agent is an antibody (e.g., a monoclonal or a polyclonal
antibody) or aptamer that specifically binds to the biomarker.
[0079] Furthermore, the present disclosure relates to a device for
predicting the risk of acute kidney injury in an at-risk patient
subjected to a surgical procedure, comprising an analyzing unit for
determining the amount of GDF-15 and/or troponin in a sample
obtained from the patient; and an evaluation unit for comparing the
determined amount with a suitable reference amount and for
predicting the risk of acute kidney damage.
[0080] The term "device" as used herein relates to a system
comprising at least the aforementioned means operatively linked to
each other as to practice the method of the present disclosure.
Suitable means for determining the amounts of the markers of the
disclosed methods, and means for carrying out the comparison are
disclosed above in connection with the disclosed methods. How to
link the means in an operating manner will depend on the type of
means included in the device. For example, where an analysis unit
for automatically determining the amount of the gene products of
the present disclosure is applied, the data obtained by said
automatically operating analysis unit can be processed by, e.g., a
computer as evaluation unit in order to obtain the desired results.
In some embodiments, the means are comprised of a single device in
such a case.
[0081] Suitable reference amounts are described herein.
[0082] In some embodiments, the device for predicting the risk of
AKI in an at-risk patient includes an analyzing unit for the
measurement of the amount of GDF-15/and or troponin in an applied
sample and an evaluation unit for processing the resulting data. In
certain embodiments, the evaluation unit comprises a database with
the stored reference amounts and a computer program code which when
tangibly embedded on a computer carries out the comparison of the
determined amounts and the reference amounts stored in the
database. In other embodiments, the evaluation unit comprises a
further computer program code that allocates the result of the
comparison to a risk prediction. In such a case, it is envisaged
that the evaluation unit comprises a further database wherein the
reference amounts are allocated to the risks.
[0083] Alternatively, where means such as test strips are used for
determining the amount of GDF-15 and/or troponin, the evaluation
unit may comprise control strips or tables allocating the
determined amount to a reference amount. In some embodiments, the
test strips are coupled to ligands that specifically bind to GDF-15
and/or troponin. In other embodiments, the strip or device
comprises means for detection of the binding of GDF-15 and/or
troponin to said ligands. Suitable means for detection are
disclosed in connection with embodiments relating to the disclosed
methods. In such a case, the analysis unit and the evaluation unit
are operatively linked in that the user of the system brings
together the result of the determination of the amount and the
diagnostic or prognostic value thereof due to the instructions and
interpretations given in a manual. The analysis unit and the
evaluation unit may appear as separate devices in such an
embodiment, and in some embodiments are packaged together as a kit.
A person skilled in the art will realize how to link the means.
Suitable devices are those that can be applied without the
particular knowledge of a specialized clinician, e.g., test strips
or electronic devices that merely require loading with a sample.
The results may be given as output of raw data, which need
interpretation by the clinician. In certain embodiments, however,
the output of the device is processed, i.e., evaluated, raw data
that does not require interpretation by a clinician. Other suitable
devices comprise the analyzing units/devices (e.g., biosensors,
arrays, solid supports coupled to ligands specifically recognizing
the gene product, plasmon surface resonance devices, NMR
spectrometers, or mass-spectrometers) or evaluation units/devices
referred to above in accordance with the methods of the
disclosure.
[0084] Moreover, the present disclosure relates to a kit for
predicting the risk of acute kidney injury in an at-risk patient
subjected to a surgical procedure, comprising an analyzing agent
for determining the amount of GDF-15 and/or troponin in a sample
obtained from the patient; and an evaluation unit for comparing the
amounts determined by the analyzing agent with a suitable reference
amount, said unit further allowing the prediction of the risk of
acute kidney damage
[0085] The term "kit" as used herein refers to a collection of the
aforementioned components that may or may not be packaged together.
The components of the kit may be comprised by separate vials (i.e.,
as a kit of separate parts) or provided in a single vial. Moreover,
it is to be understood that the kit of the present disclosure is to
be used for practicing the methods referred to herein. In some
embodiments, it is envisaged that all components are provided in a
ready-to-use manner for practicing the methods referred to above.
In certain embodiments, the kit also contains instructions for
carrying out the disclosed methods. The instructions can be
provided by a user's manual in paper or electronic form. For
example, the manual may comprise instructions for interpreting the
results obtained when carrying out the aforementioned methods using
the kit of the present disclosure. The kit shall comprise an
analyzing agent. This agent is capable of specifically recognizing
GDF-15 and/or troponin in a sample obtained from the patient.
Moreover, in some embodiments, the agent(s) shall, upon binding to
the GDF-15 and/or troponin, be capable of generating a detectable
signal, the intensity of which correlates to the amount of GDF-15
and/or troponin present in the sample. Depending on the type of
signal that is generated, methods for detection of the signal can
be applied which are well known in the art. Analyzing agents that
can be used for the kit of the present disclosure include
antibodies or aptamers. The analyzing agent may be present on a
test strip as described herein. The amounts of GDF-15 and/or
troponin detected can then be further evaluated in the evaluation
unit. Suitable evaluation units to be used for the kit of the
present disclosure include those referred to herein.
[0086] In another embodiment, the disclosed methods relate to a
method for diagnosing myocardial infarction (MI) in a patient, and
more particularly, an at-risk patient, comprising the steps of
determining the amount of troponin T in a sample of the patient;
comparing the measured amount of troponin T to a suitable reference
amount; and diagnosing whether said patient suffers from MI based
on such comparison.
[0087] Moreover, in yet another embodiment, the disclosed methods
are carried out by determining TGF-R instead of GDF-15.
[0088] The following examples, sequence listing, and figures are
provided for the purpose of demonstrating various embodiments of
the instant disclosure and aiding in an understanding of the
present disclosure, the true scope of which is set forth in the
appended claims. These examples are not intended to, and should not
be understood as, limiting the scope or spirit of the instant
disclosure in any way. It should also be understood that
modifications can be made in the procedures set forth without
departing from the spirit of the disclosure.
EXAMPLES
Example 1
Patients, Materials and Methods
[0089] A total of 126 patients undergoing coronary artery bypass
graft (CABG) surgery were included in the study. There were 68
males and 58 females in the study group, which ranged in age from
52 to 81 years and had a median age of 68 years. Serum creatinine
levels were normal in all patients. All patients were found to have
two or more vessel disease as indicated by at least one stenosis
exceeding 50% of the lumen. Patients were followed for 30 days with
respect to mortality and development of acute kidney injury.
Endpoints of the study were: acute kidney injury (AKI; creatinine
increase at least 0.3 mg/dl within 3 days after surgery), new
requirement for hemodialysis, or mortality (within 30 days after
surgery). Blood was taken before surgery and immediately thereafter
as well as at 1, 2, and 3 days after surgery. Samples were
centrifuged for 30 minutes and stored at -20.degree. C. until
analyzed.
[0090] GDF-15, troponin T, and NT-proBNP were determined with
sandwich immunoassays using COBAS-analyzers from Roche/Hitachi. The
assays comprise two monoclonal antibodies specific for the
respective polypeptide. The first of these is biotinylated and the
second one is labelled with a
Tris(2,2'-bipyridyl)ruthenium(II)-complex. In a first incubation
step, both antibodies were incubated with a patient sample, forming
a sandwich complex comprising the peptide to be assayed and the two
different antibodies. In a next incubation step,
streptavidin-coated beads were added to the sandwich complex from
the first incubation step, allowing the beads to bind to the
sandwich complexes. The reaction mixture was then aspirated into a
measuring cell where the beads were magnetically captured on the
surface of an electrode. The application of a voltage induced a
chemiluminescent emission from the ruthenium complex, which was
measured by a photomultiplier, the amount of emitted light being
dependent on the amount of sandwich complexes that were captured on
the electrode. In the sandwich immunoassays described above, GDF-15
amounts between 300 pg/ml to 20000 pg/ml, troponin T amounts
between 3 pg/ml to 10000 pg/ml, and NT-proBNP amounts between 5
pg/ml and 35000 pg/ml could be measured.
[0091] Creatinine was determined using a modification of the Jaffe
method (Foster-Swanson et al., 1994, Clin. Chem. Abstract #361;
Seelig and Wust, 1969, Arztliches Labor 15: 34-39; Bartels et al.,
1972, Clin. Chim. Acta 37: 193-97). Briefly, picrinic acid was
allowed to react with creatinine in alkaline solution to form a
yellow-orange complex. The complex was detected photometrically
using Roche/Hitachi analyzers.
[0092] The results obtained in this study are shown in Tables 1 a
to 1c and 2a to 2c below.
TABLE-US-00001 TABLE 1a GDF-15 levels before surgery Outcome No AKI
AKI Dialysis Mortality N 89 37 12 9 Median 1078 1717 2573 2442
GDF-15 [pg/ml] 25th 781 1101 1250 1626 percentile [pg/ml] 75th 1401
2448 4508 3273 percentile [pg/ml]
TABLE-US-00002 TABLE 1b Troponin T levels before surgery Outcome No
AKI AKI Dialysis N 89 37 12 Median TnT 13.34 25.52 60.89 [pg/ml]
25th 7.67 16.54 23.20 percentile [pg/ml] 75th 33.11 62.01 495.97
percentile [pg/ml]
TABLE-US-00003 TABLE 1c NT-proBNP levels before surgery Outcome No
AKI AKI Dialysis N 89 37 12 Median NT- 488.18 1385.49 2227.06
proBNP [pg/ml] 25th percentile 160.26 481.45 794.08 [pg/ml] 75th
percentile 1118.66 2485.66 3358.61 [pg/ml]
[0093] As shown in Tables 1a to 1c, the group of patients who
suffer from AKI after CABP were found to have increased median
amounts of GDF-15, troponin T, and NT-proBNP. In addition, the
median amounts of GDF-15, troponin T, and NT-proBNP before surgery
were found to be higher in patients suffering from a severe case of
AKI (requiring hemodialysis) after surgery. Thus, GDF-15, troponin
T, and NT-proBNP can be used to predict and differentiate between
different severities of AKI.
TABLE-US-00004 TABLE 2a GDF-15 levels [pg/ml] at different time
points after surgery No AKI* AKI* Dialysis* Mortality* Immediately
1807 3389 6393 5256 after surgery 1337-3467 2036-6584 3571-7653
3401-8099 1 day after 6375 11988 14507 9786 surgery 4177-8603
8393-20600 9525-22230 8605-14260 2 days after 2352 8034 8929 8930
surgery 1619-3201 3985-11748 5233-13038 5087-13774 3 days after
1903 4675 5938 5652 surgery 1487-3033 3397-7731 4366-11022
4150-8408 *Median values, 25th and 75th percentiles
TABLE-US-00005 TABLE 2b Troponin T levels [pg/ml] at different time
points after surgery No AKI* AKI* Dialysis* Immediately 312.39
593.14 640.34 after surgery 176.63-503.56 139.87-1908.04
549.87-1421.68 1 day after 863.85 1108.10 1280.91 surgery
364.48-1217.33 448.83-3612.46 500.98-5439.78 2 days after 537.61
739.07 981.30 surgery 279.53-855.98 387.11-2074.96 357.56-2006.06 3
days after 370.92 492.60 574.96 surgery 182.70-812.45
310.91-1424.18 315.58-1724.62 *Median values, 25th and 75th
percentiles
TABLE-US-00006 TABLE 2c NT-proBNP levels [pg/ml] at different time
points after surgery No AKI* AKI* Dialysis* Immediately 368.58
924.62 1933.30 after surgery 139.15-940.25 381.57-2124.55
914.53-5824.65 1 day after 1560.68 1972.22 4876.65 surgery
914.09-2565.12 1086.06-4686.00 3296.20-6485.33 2 days after 2717.21
4953.24 6597.74 surgery 1667.04-4618.54 2344.10-10839.93
2978.74-13846.26 3 days after 2825.03 4983.66 5291.93 surgery
1812.31-5393.36 2661.26-9243.66 4092.11-12000.25 *Median values,
25th and 75th percentiles
[0094] As shown in Table 2a to 2c, patients likely to experience
complications following cardiovascular surgery can also be
identified. Patients suffering from a severe case of AKI requiring
hemodialysis were found to have generally higher levels of GDF-15,
troponin T, and NT-proBNP than patients who suffered from AKI
without the need for hemodialysis. Thus, GDF-15, troponin T, and
NT-proBNP can be used to not only predict the occurrence of AKI but
also the severity of AKI.
Example 2
Individual Patient Cases
[0095] Case 1: a 62-year-old male, suffering from 3-vessel disease
with multiple stenoses, underwent CABG. He had long-standing
arterial hypertension, no diabetes mellitus or smoking history. His
lipids were in the normal range. However, this patient had a
history of obesity. The following results were obtained for this
patient before and after surgery:
TABLE-US-00007 before after 1 day after 2 days after 3 days after
surgery surgery surgery surgery surgery Creatinine 0.80 0.72 0.90
0.81 0.84 [mg/dl] GDF-15 1700 1800 5600 2900 1900 [pg/ml] TnT 12.9
316.0 582.0 416.0 352.0 [pg/ml] NT-proBNP 380 410 1420 1530 1380
[pg/ml]
[0096] The patient recovered from CABG without further
complications, with no occurrence of AKI. Before surgery, the
amounts of GDF-15 and NT-proBNP were below the reference amount
that would indicate an increased risk of AKI post surgery (1717
pg/ml and 1119 pg/ml, respectively). In addition, the amount of
troponin T indicated that an increased risk of AKI could be ruled
out (TnT below 13.3 pg/ml).
[0097] Case 2: a 58-year-old male, suffering from 2-vessel disease
with multiple stenoses, underwent CABG. He was a previous smoker,
had arterial hypertension and no diabetes mellitus. His lipids were
in the normal range. The following results were obtained for this
patient before and after surgery:
TABLE-US-00008 before after 1 day after 2 days after 3 days after
surgery surgery surgery surgery surgery Creatinine 1.15 1.08 1.40
2.1 1.6 [mg/dl] GDF-15 3200 3300 10000 13000 4100 [pg/ml] TnT 23.9
621.0 490.0 380.0 210.0 [pg/ml] NT-proBNP 1480 2010 3860 3540 3790
[pg/ml]
[0098] The patient experienced acute kidney injury, but recovered
spontaneously without need for acute dialysis. Before surgery, the
amount of GDF-15 indicated an increased risk of AKI requiring renal
replacement therapy, the amount of troponin T was just below the
threshold indicating an increased risk of AKI (25.5 pg/ml), and the
amount of NT-proBNP indicated an increased risk of AKI. Taken
together, two out of three markers indicated the presence of an
increased risk of AKI. In addition, the necessity of hemodialysis
was predicted for one marker. The occurrence of AKI in this
patient, therefore, conformed with the prediction.
[0099] Case 3: a 62-year-old male suffering from extensive 3 vessel
disease underwent CABG. He had dyspnoe before surgery and reported
episodes of symptomatic heart failure in the past that were treated
with ACE-inhibitors, beta-blockers, and diuretics. His kidney
function was marginal and changed with the use of loop diuretics.
His risk profile included smoking, arterial hypertension, and
obesity, but had recently lost weight. The following results were
obtained before and after surgery:
TABLE-US-00009 before after 1 day after 2 days after 3 days after
surgery surgery surgery surgery surgery Creatinine 1.2 1.3 1.6 3.2
4.5 [mg/dl] GDF-15 2416 5820 9210 8760 5820 [pg/ml] TnT 62.3 657.0
1380.0 975.0 612.0 [pg/ml] NT-proBNP 2480 1980 4920 6370 5910
[pg/ml]
[0100] The patient suffered from AKI post surgery and required
hemodialysis. Before surgery, the amounts of troponin T and
NT-proBNP indicated an increased risk of AKI requiring
hemodialysis, and the amount of GDF-15 was just below the reference
value indicating the risk of AKI requiring hemodialysis (2573
pg/ml). Hence, all three markers correctly predicted the occurrence
of AKI, and two of the markers also correctly predicted a severe
case of AKI requiring hemodialysis.
[0101] All publications, patents, and applications are hereby
incorporated by reference in their entirety to the same extent as
if each such reference was specifically and individually indicated
to be incorporated by reference in its entirety.
[0102] While this disclosure has been described as having an
exemplary design, the present disclosure may be further modified
within the spirit and scope of this disclosure. This application is
therefore intended to cover any variations, uses, or adaptations of
the disclosure using its general principles. Further, this
application is intended to cover such departures from the present
disclosure as come within the known or customary practice in the
art to which this disclosure pertains.
* * * * *