The Kodak Ektachem 400 Analyzer evaluated for automated enzymic determination of plasma creatinine

We have evaluated an automated creatinine iminohydrolase procedure for plasma creatinine analysis, as used in the Kodak Ektachem 400 Analyzer. The correlation with kinetic and end-point (equilibrium) alkaline picrate procedures is generally excellent. The enzymatic procedure has the advantage of being unaffected by bilirubin, cephalosporins, and acetoacetate, all of which interfere in alkaline picrate procedures. Its accuracy, however, greatly depends on calibration values provided by the manufacturer. Storage of samples at -20 degrees C produced little change in measured creatinine. The Ektachem procedure has a greater range of linearity (140 mg/L) than the alkaline picrate procedures, but it shares with them the disadvantages of suboptimal precision in the normal range. The increased specificity, ease of performance, and other advantages of this use of creatinine iminohydrolase make it an attractive procedure.