Use of Single-Value Protein Compensation of the Jaffe Creatinine Assay Contributes to Clinically Significant Inaccuracy in Results

Effective use of equations for calculating estimated glomerular filtration rate (eGFR) requires reliable plasma creatinine measurements (1). Considerable effort has been made to standardize calibration (2)(3), but standardization does not correct for analytical interferences, such as protein interference in Jaffe creatinine assays. A single-value correction factor is often used to correct for nonspecific protein interference in Jaffe assays, but this approach does not take into account differences in plasma albumin concentrations among samples. Because of the current interest in low creatinine results for calculation of eGFR, we evaluated the validity and clinical impact of using a single compensation value. We determined the dependence of creatinine results on albumin concentration by adding increasing amounts of human albumin powder to plasma specimens containing low albumin and creatinine concentrations of 50 and 340 μmol/L, respectively. We then measured, in …