Effect of detergent on kinetic Jaffé-method assay of creatinine

Using isotope dilution-mass spectrometry as reference method, we show that the kinetic Jaffé method for determination of serum creatinine sometimes produces results that are much too high. Such falsely increased values were obtained in about 10% of the sera collected for routine determination of creatinine, and were most common when certain types of collecting tubes were used. The interferences could be overcome by use of detergent in the reaction mixture.