RESUMO
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.
RESUMO
BACKGROUND: Although the automation of instruments has reduced the variability of results and errors of analysis, in some laboratories, repeating a test to confirm its accuracy is still performed for critical and noncritical results. However, the importance of repeat testing is not well established yet, and there are no clear criteria for repeating a test. MATERIALS AND METHODS: In this cross-sectional study, all repeated tests for 26 biochemical analytes (i.e., albumin, alkaline phosphatase (ALP), alanine aminotransferase (ALT), amylase, aspartate aminotransferase (AST), bilirubin total (BT), bilirubin direct (BD), blood urea nitrogen (BUN), calcium, chloride (Cl), cholesterol total (CholT), creatine kinase (CK), creatinine (Cr), glucose, gamma-glutamyl transferase (GGT), high-density lipoprotein-cholesterol (HDL-c), iron, lactate dehydrogenase (LDH), LDL-c, lipase, magnesium (Mg), phosphorus (Ph), protein total (ProtT), total iron binding capacity (TIBC), triglyceride (TG), and uric acid) were assessed in both critical and noncritical ranges over two consecutive months (routine subjective test repeats in the first month and rule-based repeats in the second month). To determine the usefulness of test repeats, differences between the initial and verified results were compared with the allowable bias, and repeat testing was considered necessary if it exceeded the allowable bias range. All causes of repeat testing, including linearity flags, delta checks, clinically significant values, and critical values, were also documented. All data, including the cause of repeats, initial and verified results, time, and costs in the two consecutive months, were transferred to Microsoft Excel for analysis. For comparison of data between the months, Student's t-test was used. RESULTS: A total of 7714 repeat tests were performed over two consecutive months. Although a significant decline (38%) was found in repeated tests in the second month (P < 0.001), there was no significant change in the percentage of unnecessary repeats (77% in the first month and 74% in the second month). In both consecutive months, AST and ALT were the most commonly repeated tests, and delta check was the most common cause of repeat testing. Mg, ALP, AST, and lipase showed the highest rates of necessary repeats, respectively (the least stable tests), while albumin, LDL, and CholT tests showed the highest rates of unnecessary repeats, respectively (the most stable tests). The total cost and delay in turnaround time (TAT) due to repeated testing decreased by 32% and 36%, respectively. CONCLUSION: Although repeat testing has been shown to be unnecessary in most cases, having a strict policy for repeat testing appears to be more valuable than avoiding it completely. Each laboratory is advised to establish its own protocol for repeat testing based on its own practice.
