Kinetic serum creatinine assays. II. A critical evaluation and review.

We have evaluated the Technicon AutoAnalyzer method, the Beckman Creatinine Analyzer II, DuPont aca, Electro-Nucleonics GEMSAEC, and Instrumentation Laboratory Model 916 kinetic methods for determination of serum creatinine. These methods, which involve the Jaffé reaction, all showed a statistically significant proportional error relative to an ion-exchange pretreatment method for creatinine in 92 serum samples; the GEMSAEC method also showed a bias. The positive interference of several acid metabolites was quantitated in each of the methods. The evidence indicates that bilirubin, although associated with a negative creatinine interference, is not the sole interferent. We determined the magnitude of this interference and studied several methods for minimizing it.