The glucose interference in creatinine measurement using an enzymatic method: effect of creatinine concentrations.

To evaluate the influence of glucose and creatinine concentrations on the determination of creatinine by Jaffe picrate reaction and specific enzymatic assay. Unused dialysate with 4.25% dextrose was diluted to obtain seven glucose concentrations. Two series of dialysate were spiked with creatinine to yield concentrations of 5 and 10 mg/dl. Creatinine measurements were obtained by Jaffe method and enzymatic assay. In unused dialysate solution with glucose concentrations from 559 to 4,250 mg/dl, the creatinine values obtained by the Jaffe method were higher than the enzymatic assay (0.31 +/- 0.20 vs. 0.08 +/- 0.01 mg/dl, p < 0.05). The correlation coefficient between glucose and creatinine from the Jaffe method were 0.98 (p < 0.001) but showed no correlation with creatinine measured with the enzymatic assay. On the other hand, the mean values of creatinine in dialysate with creatinine concentrations of 5 and 10 mg/dl derived by Jaffe method were lower than enzymatic assay (5.74 +/- 0.12 vs. 6.16 +/- 0.36 mg/ dl and 11.56 +/- 0.17 vs. 12.69 +/- 0.66 mg/dl, respectively). At creatinine concentration of 10 mg/dl, the correlation between glucose concentration and creatinine from enzymatic assay was significant. In contrast, at creatinine concentration of 5 mg/ dl, the correlations obtained from both methods were significant. The patterns of glucose interference with creatinine obtained from Jaffe method and enzymatic assay were quite different. The magnitude of interference with enzymatic assay was greater at a higher creatinine concentration. Therefore, the enzymatic assay might not be appropriate for creatinine measurement in patients using dialysate with dextrose 4.25% and membrane characteristic of high solute transporter.