Impact of different creatinine measurement methods on liver transplant allocation

Comparing Jaffe and Enzymatic Methods for Creatinine Measurement at Various Icterus Levels and Their Impacts on Liver Transplant Allocation

The Model for End-Stage Liver Disease (MELD) scoring system is used to prioritize liver transplantations and assess disease severity. This includes the international normalized ratio (INR), creatinine, and total bilirubin. Since there are several ways to measure creatinine, MELD scores can produce inconsistent results. The objectives of this study were to define a valid cut-off for bilirubin interference in creatinine measurement and to assess the effects of various icteric levels on creatinine measurement and liver transplant allocation. A total of 400 serum samples were categorized into four groups based on their icteric indices and total bilirubin levels, including non-, mild, moderate, and severe icteric samples. Both chemical Jaffe and enzymatic techniques were used to determine the creatinine levels in all four groups, and the findings were compared. In parallel, serum samples from 83 liver transplant candidate patients were divided into three groups depending on their bilirubin levels and then similarly evaluated and interpreted. The MELD scores were then computed for each group and compared. In icteric samples, the enzymatic method produced higher results for the creatinine concentrations than the Jaffe method did, and the mean creatinine difference rose from 0.08 in nonicteric group to 1.95 in groups with severe icterus. In addition, the enzymatic approach yielded higher findings for creatinine and subsequently for MELD scores in patients who were liver transplant candidates. When the bilirubin concentration was above the 4 mg/dL threshold, there were differences between the approaches for both the creatinine and the MELD score (p values: 0.0001 and 0.027, respectively). The chemical Jaffe is a readily available and considerably cost-effective method for measuring creatinine. However, it is influenced by a variety of known and unknown interfering substances, and it should be applied cautiously when working with icteric samples. Alternate techniques such as the enzymatic method should be considered when the bilirubin level exceeds 4 mg/dL. Though this cut-off is instrument and kit-dependent, each laboratory is advised to have its cut-off for bilirubin interference.

Experiences from six years of quality assured Model of End Stage Liver Disease (MELD) diagnostics

BACKGROUND

The model of end-stage liver disease (MELD) score was established for the allocation of liver transplants. The score is based on the medical laboratory parameters: bilirubin, creatinine and the international normalized ratio (INR). A verification algorithm for the laboratory MELD diagnostic was established, and the results from the first six years were analyzed.

METHODS

We systematically investigated the validity of 7,270 MELD scores during a six-year period. The MELD score was electronically requested by the clinical physician using the laboratory system and calculated and specifically validated by the laboratory physician in the context of previous and additional diagnostics.

RESULTS

In 2.7% (193 of 7,270) of the cases, MELD diagnostics did not fulfill the specified quality criteria. After consultation with the sender, 2.0% (145) of the MELD scores remained invalid for different reasons and could not be reported to the transplant organization. No cases of deliberate misreporting were identified. In 34 cases the dialysis status had to be corrected and there were 24 cases of oral anticoagulation with impact on MELD diagnostics.

CONCLUSION

Our verification algorithm for MELD diagnostics effectively prevented invalid MELD results and could be adopted by transplant centers to prevent diagnostic errors with possible adverse effects on organ allocation.

Frailty as a predictive factor for survival after liver transplantation, especially for patients with MELD≤15-a prospective study

Introduction

Frailty has been discussed as a predictor of morbidity and mortality for liver cirrhosis. The aim of our study is to evaluate the role of frailty in liver transplantation, particularly for patients with MELD scores < 15.

Methods

All patients listed for liver transplantation between September 2015 and November 2018 were prospectively included in the study. Frailty was assessed by Fried’s frailty classification. Pre-, intra-, and postoperative data were prospectively recorded. Univariate and multivariate regression analyses were performed. The ethical approval of the institutional board review was obtained for the study.

Results

There were 114 patients included in the study, and their median MELD score was 16. Of these, 86 patients were defined as frail (75.4%). A total of 62 patients (54.4%) underwent liver transplantation, 11 (17.7%) died postoperatively, and 24 patients (21.0%) died while on the waitlist. All postoperative mortality cases were frail, and only 3 patients (12.5%) were non-frail in the waitlist mortality group. There were 14 patients who had MELD scores of <15 (58.3%). The overall survival of non-frail patients was significantly better than that of frail patients. The multivariate regression analyses identified frailty criteria, including unintended weight loss and low hand grip strength, and platelet count and being married or living in a solid partnership were prognostic factors for survival in all patients.

Conclusion

The addition of frailty assessment can be beneficial for predicting mortality after liver transplantation, especially in patients with low MELD score. Frail patients on the waitlist have significant risk for mortality even with low MELD score.

When results matter: reliable creatinine concentrations in hyperbilirubinemia patients

Background

Failure to report a creatinine concentration, especially in icteric patients who are eligible for a liver transplant, can result in a life-threatening situation. We assessed the influence of bilirubin interference on several creatinine assays and investigated ways to circumvent icteric interference without interfering with our normal automated sample logistics.

Methods

Using icteric patient sera (total bilirubin >255 μmol/L) we determined creatinine concentrations using an enzymatic and Jaffé assay (Roche Diagnostics) in both normal (i.e. undiluted) and decreased mode (i.e. diluted) as well as an enzyme-coupled amperometric assay on a Radiometer ABL837 FLEX analyzer. Creatinine concentrations from the five methods were compared with an in-house developed LC-MS/MS method. Passing and Bablok (proportional and constant bias) as well as difference plot parameters (bias and 95% limits of agreement [LoA]) were calculated. Interferograph-based regression analysis of the enzymatic and Jaffé results was used to investigate if such an approach could be used to report corrected creatinine concentrations in icteric patient sera.

Results

In icteric patient sera the enzyme-coupled amperometric assay was hardly influenced by icteric interference as shown by a difference plot bias of −1.5% (95% LoA −11.6 to +8.5%). The undiluted Jaffé method had a bias of −1.4% with a very broad 95% LoA (−35.1 to +32.2%) emphasizing the poor specificity of this method. The undiluted enzymatic method had the largest bias (−13.4%, 95% LoA −35.8 to +9.0%). Diluting sera in the enzymatic method did not improve the bias (−10.5%, 95% LoA −25.4 to 4.4%), while diluting the Jaffé method resulted in a bias increase (+11.4%, 95% LoA −14.7 to 37.5%). Using interferograph-based regression analysis we were able to reliably correct enzymatic creatinine concentrations in 97 out of 100 icteric patient sera.

Conclusions

Analytically, quantifying creatinine in icteric sera using the Radiometer ABL837 FLEX analyzer is the method of choice within our laboratory. However, not all laboratories are equipped with this method and even if available, the limited number of highly icteric patient sera makes this method costly. For those laboratories using the Roche enzymatic method, mathematically correcting an icteric creatinine concentration using an interferograph based on an LC-MS/MS reference method is a suitable alternative to report reliable creatinine results in icteric patients.

Limited comparability of creatinine assays in patients with liver cirrhosis and their impact on the MELD score

BACKGROUND & AIM

Patients with end-stage liver disease require valid estimations of mortality for organ allocation and risk stratification. The model of end-stage liver disease (MELD) score is used for this purpose in most countries and incorporates bilirubin, International Normalized ratio, and creatinine. The aim of this study was to evaluate the comparability of creatinine results from different routine assays in the serum samples of patients with liver cirrhosis.

METHODS

Residual material from 60 serum samples was available from patients in different stages of liver cirrhosis. Four centers participated; each center analyzed the samples with Jaffé-based and enzymatic routine assays in parallel. In addition, an accredited calibration laboratory certified the panel of samples by an internationally accepted reference measurement procedure (RMP) based on isotope dilution mass spectrometry (ID-MS). This method served as the independent reference.

RESULTS

All routine methods displayed a high correlation to the RMP (r ≥0.937, p<0.001). Two enzymatic and two Jaffé-based methods provided results that were all within a ±20% range of the RMP. The other methods showed deviations >20% in up to 27% of the samples. The enzymatic methods were systematically lower, whereas the Jaffé-based methods were systematically higher (p<0.001). The resulting MELD scores differed from 0 to 4 points.

CONCLUSIONS

There are systematic deviations from the RMP. Jaffé-based assays gave higher results, whereas the enzymatic-based assays gave lower results compared to the results of the RMP. The comparability of results is limited and could be disadvantageous to patients listed for liver transplantation.

Performance Characteristics of Kidney Injury Molecule-1 In Relation to Creatinine, Urea, and Microalbuminuria in the Diagnosis of Kidney Disease

Context:

The diagnosis and evaluation of impaired renal function remains a challenge owing to lack of reliable biomarker for assessment of kidney function. The existing panel of biomarkers currently displays several limitations, and recently kidney injury molecule-1 (KIM-1) has been suggested as a sensitive biomarker of renal function and proposed to enter clinical practice.

Aims:

This study was conducted to determine the diagnostic value of serum creatinine, urea, and microalbuminuria (MAU) in relation to the novel biomarker, KIM-1.

Materials and Methods:

Serum creatinine, urea, MAU, and KIM-1 were measured in forty individuals with and forty without kidney disease. Data were analyzed using multivariate methods of assessing diagnostic efficiency, test agreement, condition effects, and variability.

Results:

The area under the receiver-operator characteristic curve revealed a diagnostic advantage of creatinine (0.924 ± 0.0066) and urea (0.925 ± 0.0068) over MAU (0.880 ± 0.078) and KIM-1 (0.35 ± 0.124). Overall diagnostic efficiency was higher for creatinine and urea (89.5% and 90.9%, respectively), followed by MAU (85.7%) and then KIM-1 (56.3%). Logistic regression analysis showed that creatinine and urea (R² = 0.75 and R² = 0.72, respectively, P < 0.001 for both) were better predictors of kidney disease than MAU (R² = 0.64, P < 0.001) and KIM-1 (R² = 0.046, P = 0.116). Further analysis of agreement showed that urea had an excellent agreement with creatinine (kappa r = 0.835, P < 0.001), with KIM-1 (kappa r = –0.198, P = 0.087) showing a poor agreement with creatinine.

Conclusion:

Our results indicate that elevated serum creatinine and urea above specific cutoff points reliably identifies patients with acute kidney injury or chronic kidney disease. However, more researches are warranted to further validate the diagnostic efficiency and application of MAU and for KIM-1 before its implementation in clinical practice.

LC-MS/MS Method for Serum Creatinine: Comparison with Enzymatic Method and Jaffe Method

Accurate quantification of creatinine (Cre) is important to estimate glomerular filtration rate (GFR). Differences among various methods of Cre quantification were previously noted. This study aims to develop a liquid chromatography tandem mass spectrometry (LC-MS/MS) method for serum Cre and compare this method with clinical routine methods. LC-MS/MS analysis was performed on API 4000 triple quadrupole mass spectrometer coupled with an Agilent 1200 liquid chromatography system. After adding isotope-labeled Cre-d3 as internal standard, serum samples were prepared via a one-step protein precipitation with methanol. The LC-MS/MS method was compared with frequently used enzymatic method and Jaffe method. This developed method, with a total run time of 3 min, had a lower limit of quantification of 4.4 μmol/L, a total imprecision of 1.15%–3.84%, and an average bias of 1.06%. No significant matrix effect, carryover, and interference were observed for the LC-MS/MS method. The reference intervals of serum Cre measured by LC-MS/MS assay were 41–79 μmol/L for adult women, and 46–101 μmol/L for adult men. Using LC-MS/MS as a reference, the enzymatic method showed an average bias of -2.1% and the Jaffe method showed a substantial average bias of 11.7%. Compared with the LC-MS/MS method, significant negative bias was observed for the enzymatic and Jaffe methods in hemolytic and lipimic samples. We developed a simple, specific, and accurate LC-MS/MS method to analyze serum Cre. Discordance existed among different methods.