Bilirubin and metamizol do not interfere with the randox enzymatic creatinine test. An evaluation of a new enzymatic creatinine determination method.

We evaluated the new commercially available enzymatic test kit for creatinine (Randox Laboratories Ltd. Ardmore, Crumlin, UK). The test correlated well with the reference HPLC method (yenz = 0.98x + 1.4; r = 1.00; n = 72). The correlations with the Jaffe method (yenz = 1.00x + 14.1; r = 0.99; n = 72) and the dry slide technique (yenz = 1.07x + 4.1; r = 1.00; n = 72) were also good, but these techniques gave slightly higher creatinine results than the HPLC or the Randox enzymatic method. This new test is insensitive to bilirubin interference. It has been reported that patients receiving metamizol showed unusually low values of creatinine, when determined enzymatically, but this drug does not interfere with the Randox method. The test evaluated is more specific than enzymatic methods published earlier and it provides an attractive alternative to the traditional picrate test.