Impact of standardized calibration on the inter-assay variation of 14 automated assays for the measurement of creatinine in human serum.
OBJECTIVE
The aim of our study was to measure the inter-assay variation and accuracy of serum creatinine assays and to assess the effect of standardized calibration procedures on this variability.


METHODS
We analyzed 30 human sera and three reference materials, using 17 creatinine assays (12 colorimetric, 4 enzymatic and 1 HPLC). We compared two standardized calibration procedures, using either a reference material or secondary standards, to that recommended by the manufacturers.


RESULTS
For assays calibrated according to the manufacturers' recommendations, the median inter-assay coefficient of variation (CV) was 14.2% for 20 low samples (45-150 microM), and 7.7% for 10 high samples (250-350 microM). The CV was significantly influenced by the calibration procedure, but none of the standardized calibration procedures significantly improved the inter-assay variability. However, a significant decrease in CV was noted within each type of assay method (colorimetric or enzymatic) when the standardized calibration used standards of level(s) close to the concentrations to be measured. Only the compensated Jaffe technique and the amido-hydrolase assay showed bias of less than 10%.


CONCLUSIONS
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.
Séronie-Vivien
Sophie
S
Institut Claudius Regaud, Toulouse, France. seronie@icr.fnclcc.fr
Galteau
Marie-Madeleine
MM
Carlier
Marie-Christine
MC
Hadj-Aissa
Aoumeur
A
Hanser
Anne-Marie
AM
Hym
Bernadette
B
Marchal
Alain
A
Michotey
Odile
O
Pouteil-Noble
Claire
C
Sternberg
Michel
M
Perret-Liaudet
Armand
A
D001331:Automation; D001774:Blood Chemical Analysis / Q000379:methods* / Q000592:standards*; D002138:Calibration; D003404:Creatinine / Q000097:blood*; D006801:Humans; D015203:Reproducibility of Results
D003404:Creatinine