Komenda P et al. (2007) Regional implementation of creatinine measurement standardization. J Am Soc Nephrol 19: 164–169

Estimation of glomerular filtration rate (GFR) is generally dependent on creatinine-based equations. Many health professionals fail to recognize that variability in the results of serum creatinine measurement between laboratories can affect diagnoses. Creatinine measurement can be standardized by use of isotope dilution mass spectrometry. Komenda et al. report on the implementation of a voluntary standardization program in 107 clinical laboratories in the Canadian province of British Columbia that routinely measured creatinine levels by use of 124 analyzers from 6 different manufacturers.

The accuracy of testing was assessed by comparing the values obtained from analysis of a common set of human serum samples (creatinine levels between 50 and 130 µmol/l [0.6–1.5 mg/dl]) in individual laboratories with those obtained by isotope dilution mass spectrometry in a separate analysis facility. Each laboratory was then provided with a correction factor to standardize all its test results before estimation of GFRs with the Modification of Diet in Renal Disease (MDRD) equation. The average total error in creatinine measurements before standardization was 23.9%; this fell to 8.7% after the program was implemented. The average bias (as overestimation of creatinine concentration) fell from 16.5% to 2.7%.

The authors conclude that standardization is feasible and effective, and they predict that implementing this program on a larger scale could reduce the rate of incorrect classification of stage 3 chronic kidney disease by 84%. They stress that although substantial upfront and maintenance costs are incurred in achieving laboratory standardization, these are far outweighed by the financial and human costs of patient misclassification.