Impact of standardized calibration on the inter-assay variation of 14 automated assays for the measurement of creatinine in human serum

Abstract

Standardizing calibration procedures is unlikely to decrease the analytical variability of creatinine assays enough to allow uniform and reliable use of the equations for estimation of glomerular filtration rate.

A multicentric evaluation of IDMS-traceable creatinine enzymatic assays

“…In this study, only one level of creatinine was studied and the statistical weight of methods differ from each other allowing the number of laboratories using a methodanalyzer combination (for example, the picrate method from Roche is used by 78 laboratories whereas the picrate method from Olympus is only used in 12 laboratories) [5]. Other studies in France [4] and United Kingdom [18] have also underlined the lack of standardization and the high inter-assay and inter-laboratory CV.…”

“…A panel of five serum pools was prepared in a central laboratory (Pr Galteau, Centre de Médecine Préventive, Nancy, France) in order to cover a wide range of creatinine concentrations from 40 to 200 μmol/L, as previously described [4]. During the preparation, sCr was measured using the local non compensated Jaffe assay (Olympus AU 640 using Olympus reagents).…”

“…In 2002, the "Creatinine French Working Group" demonstrated that a very high inter-assay variation persisted and that a standardization of the calibration procedure did not reduce enough the variability of sCr assays to allow reliable use of estimated GFR [4]. By the same way, a study performed in 2003 by the College of American Pathologists (CAP) evaluated on fresh frozen serum with a sCr concentration 79.7 μmol/L (0.902 mg/dL), to verify commutability among sCr measurement methods.…”

Renal Dysfunction and Liver Transplantation

“…It should also be noted that the relationship between the serum creatinine and GFR is not linear; at high levels of GFR, the Scr is insensitive to large changes in GFR, while at low levels of GFR, small changes in GFR cause large changes in serum creatinine (Mariat et al, 2004). A problem, not often recognized is that measurement of Scr suffers from a variety of interferences (Cholongitas et al, 2007 b) and absence of international standard for measurement (Seronie-Vivien et al, 2005). Serum creatinine is usually measured by the Jaffè method, but this is prone to interference, for example, from protein, ketones and bilirubin.…”

Trueness verification of actual creatinine assays in the European market demonstrates a disappointing variability that needs substantial improvement. An international study in the framework of the EC4 creatinine standardization working group

“…Since Jaffe (12) only observed a complexation between picric acid and creatinine in alkaline environment and never described an analytical method, variation among Jaffe method formulas is broad (13,14). The reference methods and materials included in the reference systems required in the IVD directive should reduce inter-laboratory variation.…”