MULTICENTER EVALUATION OF AN ENZYMATIC METHOD FOR CREATININE DETERMINATION USING A SENSITIVE COLOR REAGENT

  • 1 November 1986
    • journal article
    • research article
    • Vol. 24  (11) , 889-902
Abstract
A new enzyme colorimetric method for the determination of creatinine in serum and urine (Creatinine PAP, Cat, No. 83944 and 836885. Boehringer Mannheim GmbH, Mannheim, FRG) was evaluaed in 16 clinical chemistry laboratories and the manfacturer''s testing laboratory. The rest is based on the enzymatic degradation of creatinine and its reaction products by creatininase, creatinase and sarcosine oxidase. The H2O2 produced by the oxidation of sarcosine is determined using a modified Trinder reaction. The test can be carried out either manually or in mechanized analysers which enable the pipetting of a starter reagent to be made. The following results are obtained: 1. Depending on the analyte concentration (range 40 to 1240 .mu.mol/l), medians for the coefficients of variation were: 4.6-0.9% within-run and 6.4-2.8% between-day. At 546 nm the linear measuring range extended from 13 .mu.mol/l (detection limit) to 1780 .mu.mol/l, at 510 nm from 9 to 890 .mu.mol/l. Recoveries in aqueous and human serum based standards as well as method comparisons with Fuller''s earth methods and an enzymatic UV test indicate a high accuracy of this new enzymatic method in serum and urine. No interference was observed with haemolysed and lipaemic sera. This also applied to anticoagulants and to 36 drugs at therapeutic concentrations, with the exception of calcium dobesilate, which led to decreased values. Icteric samples containing 120-310 .mu.ml/l bilirubin invariably ledto decreased creatinine values (10-50 .mu.mol/l lower). In a collaborative study substantially better interlaboratory agreement was observed with the new colorimetric enzymatic test than with the comparison methods (enzymatic UV test and various Jaffe procedures). In conclusion, this ew enzymatic colorimetric test permits a precise and specific determination of creatinine in serum and urine. It makes a considerable contribution to improving the interlaboratory comparability of creatinine determinations and is suitable for routine use.

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