Background: The CCQM-K80 Key Comparison directly assessed the equivalence of many of the worlds higher-order value-assigned materials (HOVAMs) for creatinine in human serum. This 2009 international study compared the certified values and uncertainties of the materials using measurements made under repeatability conditions. Methods: The study evaluated 17 materials submitted by six national metrology institutes (NMIs). The creatinine quantity in these materials ranged from 3 mg/kg to 57 mg/kg (about 0.3 mg/dL to 6 mg/dL or 30 nmol/L to 500 nmol/L). All materials were stored and prepared according the specifications provided by the participating NMIs. Samples were processed and analyzed under repeatability conditions by one analyst using isotope-dilution liquid chromatography-mass spectrometry in two measurement campaigns. The certified values and repeatability measurements were compared using uncertainty-weighted generalized distance regression. Results: The instrumental repeatability relative standard deviation was 1.2 %. The measurement design required assessment of within-unit and between-campaign variability in addition to measurement repeatability. At a 95 % level of confidence, the certified values for all 17 materials agreed to within their assigned uncertainties. Conclusion: CCQM-K80 demonstrated the metrological equivalence of the currently available HOVAMs for creatinine in human serum and of the creatinine measurement services provided by the participating NMIs.
Citation: Analytical and Bioanalytical Chemistry
Pub Type: Journals
creatinine, reference material, international comparison