The Effect of Bilirubin on Laboratory Investigations on Serum Creatinine: A Comparison Study Between Jaffe Reaction and Creatinase Enzymatic Method With Creatinine in Phosphate Buffered Saline Solution and Serum

Objective: To determine the creatinine concentration in phosphate buffered saline solution and serum with different bilirubin concentrations using Jaffe reaction and Creatinase method. Methods: In Phase 1, creatinine and bilirubin concentrations in the dilution series were 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 mg/dL and 0, 3, 6, 9, 12, 15, 18, 21, 24, 27, 30 mg/dL, respectively. Each creatinine concentration was spiked with eleven bilirubin concentrations used in Phase 1. In Phase 2, serum with creatinine values 0.51, 2.41 and 7.33 mg/dL were spiked with 11 bilirubin concentrations. The total bilirubin, creatinine by Jaffe reaction and Creatinase method were measured. Results: In Phase 1, Jaffe reaction showed a significant underestimation up to creatinine concentration of 2 mg/dL at all bilirubin concentrations. From 3 mg/dL onwards, a significant overestimation was observed with high bilirubin concentrations. In Phase 2, Creatinase method gave no significant underestimation in serum with 0.51 mg/dL of creatinine. But Jaffe reaction showed a significant underestimation from bilirubin concentration of 7.18 mg/dL. In serum with 2.41 mg/dL creatinine, Creatinase and Jaffe methods gave significant underestimations from bilirubin concentrations of 9.05 and 5.64 mg/dL, respectively. In serum of 7.33 mg/dL creatinine, significant underestimations were given from bilirubin levels of 3.6 and 8.18 mg/dL by Creatinase and Jaffe methods, respectively. Conclusion: In normal to moderately high bilirubin concentrations the Creatinase method is more accurate than the Jaffe method in all creatinine concentrations used. At high creatinine concentrations Creatinase method gave significant underestimations which increased with bilirubin concentration.