Method for the early detection of acute kidney injury in critical patients, using fibroblast growth factor 23, klotho and erythropoietin as biomarkers

Abstract

The invention is an ex vivo method for early detection of acute kidney injury in critical patients, which includes the measurements of fibroblast growth factor 23 (FGF23), klotho (KL) and erythropoietin (EPO) as biomarkers. These measurements are obtained from a venous blood sample or urine, and allow the determination of the following indicators: 1=([FGF23]p×[EPO]p); 2=([FGF23]p/[Klotho]p); 3=([EPO]p)/[Klotho]p); 4=([FGF23]p×[EPO]p)/[Klotho]p); where [X]p is defined as the plasma level of a specific molecule (X) which includes fibroblast growth factor 23 (FGF23), klotho (KL) or erythropoietin (EPO). If the value of the indicator 1, 2, 3, 4 or two or more thereof, is equal or higher than a cut-off point (10 U), the indicator and/or indicators allow the identification of patients with high risk of developing AKI, with a high sensitivity/specificity. Therefore high levels of the indicator are associated to a high probability of the presence/development of AKI, which allows to perform specific clinical interventions for patients with AKI. If the value of the indicator 1, 2, 3, 4 or two or more thereof, is lower than the previously mentioned cut-off point, the probability of presence/development of AKI is low, therefore patients require only standard treatment.

Claims

1. A method for diagnosing and treating early acute kidney injury (AKI), the method comprising: a) obtaining at least one plasma sample from a patient; b) performing an immunoassay on the at least one plasma sample to determine the levels of fibroblast growth factor 23 (FGF23), Klotho and Erythropoietin (EPO); c) calculating an indicator value, wherein the indicator value is determined by the equation ((FGF23.sub.p×EPO.sub.p)/Klotho.sub.p) wherein FGF23.sub.p is the plasma level of FGF23, EPO.sub.p is the plasma level of EPO, and Klotho.sub.p is the plasma level of Klotho; d) determining said patient has AKI when the indicator value is equal to or higher than a cut-off point of 10-U; and e) treating the patient determined to have AKI by administering crystalloid solutions and restricting the patient's use of nephrotoxic drugs.

2. The method of claim 1, wherein treating at step e) further includes administering early emergency dialysis.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 shows the average lethality of AKI (as average) and AKIN3 (severe form), compared to other conditions of high morbidity and mortality such as sepsis (severe infection) and myocardial infarction (AMI).

(2) FIG. 2 shows the delayed response increase creatinine (current method to detect AKI), as compared to the decrease in renal function (GFR). (Adapted from: Star RA Treatment of acute renal failure Kidney Int 1998; 54: 1817-1831

(3) FIG. 3 shows an algorithm for the measurement and implementation of the present invention. Briefly, in patients admitted to ICU blood and urine samples will be obtained for measurement of biomarkers (FGF23, Klotho, EPO) and calculation of combined indicators. Then, according to the results, the risk of the presence/development of AKI will be calculated, and according to this risk, specific clinical recommendations will be delivered to the physician responsible of the patient.

(4) FIGS. 4A-4N shows the results of the measurements of plasma levels of FGF23×EPO/Klotho (A-B), FGF23 (C-D), EPO (E-F), Klotho (G-H), EPO/Klotho FGF23×EPO (K-L) and EPO/Klotho (M-N), according to the presence/absence of AKI, and severity of AKI. These data shows that the combined parameters increase significantly in patients with AKI, with an increase proportionally to the severity of renal injury.

(5) FIGS. 5A-5E shows the ROC curve, sensitivity and specificity of FGF23 (A), FGF23/Klotho (B), FGF23×EPO (C), EPO/Klotho (D) and FGF23×EPO/Klotho (E) to detect the presence/development of AKI in critically ill patients, at the admission to the Intensive Care Unit.

(6) FIG. 6 shows the global survival curve of critically ill patients with sepsis, stratified with high or low levels of the combined parameter during the first 30 days of hospital admission. We found that high levels of the combined parameter are associated to increased 30-day mortality.

DETAILED DESCRIPTION OF THE INVENTION

(7) For example, the ex vivo method of the present invention can be applied in critically ill patients admitted to the ICU due to severe disease (severe infections, severe burns, post highly complex surgeries, cerebral infarction, etc.). These patients are subjected to extraction of venous blood samples

(8) The extraction of blood samples is performed by a standard procedure applicable to this type of patient, then the sample will be carried to a clinical or research laboratory, where the extraction of plasma will is performed. Thus, samples can be analyzed by ELISA technique (their acronym, Enzyme-Linked ImmunoSorbent Assay) for the determination of plasma levels of FGF23, Klotho and Erythropoietin. Levels that may be available during the first hours after the admission of the patient.

(9) Plasma levels (here in after referred to only as levels) thus obtained are incorporated in the following indicators to determinate the probability to develop AKI:

(10) Indicators:

(11) 1=([FGF23].sub.p×[EPO].sub.p)

(12) 2=([FGF23].sub.p/[Klotho].sub.p)

(13) 3=([EPO].sub.p)/[Klotho].sub.p)

(14) 4=(([FGF23].sub.p×[EPO].sub.p)/[Klotho]).sub.p) where [X].sub.p is defined as the plasma level of a specific molecule (X), which includes fibroblast growth factor 23 (FGF23), Klotho and Erythropoietin (EPO).

(15) If the indicator value 1, 2, 3, 4 or two or more thereof, is higher or equal to a cut-off point (10U) that, there is a high probability of presence/development of AKI, which may allow to perform specific therapies for the management/prevention of AKI. If the indicator value 1, 2, 3, 4 or two or more of thereof is lower than the cut-off point, the probability of presence/development of AKI is low and patients would only require standard therapies.

(16) FIGS. 5A-5N show ROC analysis (their acronym, Receiver Operating Characteristic) obtained by the inventors, which determines the sensitivity and specificity of the indicators. These results show that combined parameters have high sensitivity and specificity to predict the presence/development of AKI.

(17) The combined parameters also determine whether the patient has a high or low probability to require vasoactive drugs (medications given to patients with very low blood pressure to normalize it) or dialysis during the hospitalization. Also, survival analysis indicate that patients with high levels of the combiner parameter have increased mortality compared to those with lower levels, as represented in Kaplan-Meier analysis (FIG. 6).

(18) This data would be available during the early hours of the patient, so that could be defined in advance, the measures to take to prevent the development of kidney damage in patients with high risk of presence/development of AKI.

(19) In the following section, we present 3 examples where the parameter could be useful.

EXAMPLE 1

(20) Patient Characteristics: Patient admitted to the critical care unit coming from the emergency department or hospitalized in a non-critical unit, with a diagnosis of severe sepsis/septic shock, polytrauma or acute coronary syndrome (conditions with increased risk to develop AKI).

(21) Sampling time: Upon entry of hospital, a sample of venous blood and urine is taken.

(22) Sample processing: Plasma extraction and measurement of the concentration of FGF23, Klotho and Erythropoietin, to obtain results in a few hours

(23) Analysis of results: Determination of plasma levels and results of combined indicators, that is, 1=(FG23 value×EPO value), 2=(FGF23 value/Klotho value), 3=(EPO value/Klotho value) and 4=((FGF23 value×EPO value)/Klotho value). The result would be used to determinate a treatment recommendation, based in the indicator value (greater or less than 10U).

(24) Possible actions: 1) less than 10U (cutoff) value indicator: Maintain standard therapy without adding crystalloid solutions without restriction potentially nephrotoxic drugs. 2) greater or equal than 10U indicator value: Maintain standard therapy, add crystalloid solutions, restrict use of potentially nephrotoxic drugs, and optionally, making early emergency dialysis.

(25) Reevaluation of patient: Extraction of blood samples at 24 and 48 hours, with reassessment of the value of the indicator and redefine behaviors to follow.

EXAMPLE 2

(26) Patient Characteristics: Patient hospitalized in a noncritical unit, with diagnosis of severe sepsis, heart failure, liver failure, chronic kidney disease, coming from Emergency Service

(27) Sampling time: At admission to hospital, an extraction of venous blood and urine samples will be performed.

(28) Sample processing: Plasma extraction and measurement of the concentration of FGF23, Klotho and Erythropoietin, to obtain results in a few hours.

(29) Analysis of results: Determination of plasma levels and results of combined indicators, that is, 1=(FGF23 value×EPO value), 2=(FGF23 value/Klotho value), 3=(EPO value/Klotho value) and 4=((FGF23 value×EPO value)/Klotho value). The result would be used to determinate a treatment recommendation, based in the indicator value (greater or less than 10U).

(30) Possible actions: 1) less than 10U (cutoff) value indicator: Maintain standard therapy without adding crystalloid solutions without restriction potentially nephrotoxic drugs. 2) greater or equal than 10U indicator value: Consider transfer to critical care unit likely given poor medical evolution, add crystalloid solutions, restrict use of potentially nephrotoxic drugs, and optionally, making early emergency dialysis.

(31) Reevaluation of patient: Extraction of blood samples at 24 and 48 hours, with reassessment of the value of the indicator and redefine behaviors to follow.

EXAMPLE 3

(32) Patient Characteristics: Patient admitted to the Intensive Care Unit after medium or high complexity surgery (heart surgery, vascular surgery, abdominal surgery, neurosurgery). Sampling time: After admission of ICU, a sample of venous blood and urine is taken.

(33) Patient Characteristics: Patient admitted to the Intensive Care Unit after medium or high complexity surgery (heart surgery, vascular surgery, abdominal surgery, neurosurgery). Sampling time: After admission of ICU, a sample of venous blood and urine is taken.

(34) Analysis of results: Determination of plasma levels and results of combined indicators, as mentioned in Example 1. The result would be used to determinate a treatment recommendation, based in the indicator value (greater or less than 10U.

(35) Possible actions: 1) Lower than breakpoint indicator value: Maintain standard therapy without adding crystalloid solutions without restriction potentially nephrotoxic drugs. 2) Higher or equal than cutoff indicator value: Maintain standard therapy, add crystalloid solutions, restrict use of potentially nephrotoxic drugs, and optionally, making early emergency dialysis.

(36) Reevaluation of patient: Taking further blood samples at 24 and 48 hours, with reassessment of the value of the indicator and redefine behaviors to follow.