Serum Creatinine Measurement: Do We Need to Change to an Enzymatic Assay?

The 2 assays available for measurement of creatinine include picric acid based Jaffe method and enzymatic method. Jaffe method is susceptible to interference by non-creatinine chromogens such as protein, glucose, ascorbic acid, cephalosporin, keto acids. Although, enzymatic method is less prone to interferences, it is considerably more expensive. In this study, assay performance of Jaffe and enzymatic methods for serum creatinine measurement were compared using routine 493 samples at a tertiary care hospital in Sri Lanka. Serum creatinine level was measured by both Jaffe and enzymatic assays while total protein, bilirubin and glucose levels of each sample were also measured. Creatinine concentration of routine specimens ranged from (30-1017 [micro]mol/L. The correlation coefficient (R2) for serum creatinine between the 2 methods was 0.9529. The Jaffe method gave higher creatinine results than the enzymatic method with a mean bias of 5.9 [micro]mol/L. The difference between the 2 assay methods was significant in higher creatinine concentrations according to the Bland-Altman plot with a more positive bias in Jaffe method compared to enzymatic assay. The average total protein, bilirubin and glucose concentrations in the routine samples were 72.8 g/L, 12.46 [micro]mol/L, and 111.28 mg/dL respectively. According to the bias plots, both positive and negative biases were seen with lower glucose values (200 mg/dL). The biases were evenly distributed among different levels of protein and bilirubin in the routine samples. However, all values had clinically acceptable percentage bias (