Interlaboratory Comparison with a Reference Measurement Procedure (RMP) for Determining 24,25-Dihydroxvitamin D3 in Human Serum using Liquid Chromatography - Tandem Mass[...]

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Abstract

An interlaboratory comparison study was conducted among five laboratories for determination of 24,25-dihydroxyvitamin D3 [24,25(OH)2D3] in human serum using liquid chromatography - tandem mass spectrometry (LC-MS/MS) methods. The Centers for Disease Control and Prevention (CDC), Imperial College Healthcare NHS Trust, University College Cork, University of Liège, and University of Washington analyzed 50 single-donor samples and two new Standard Reference Materials (SRMs®). The results from each laboratory were compared with target values assigned by the National Institute of Standards and Technology (NIST) using a reference measurement procedure (RMP) and evaluated using Ordinary Deming linear regression and Bland-Altman analysis. Three of the five laboratory methods provided results that were in good agreement with the NIST RMP results, i.e., linear regression slopes of 0.972 to 1.003 and Bland-Altman mean bias of -0.092 nmol/L to 0.035 nmol/L. Two laboratories demonstrated a significant positive bias with linear regression slopes of 1.158 and 1.214 and Bland-Altman mean bias of 0.162 nmol/L and 0.708 nmol/L. The CDC method is currently used to assign "information only" values for 24,25(OH)2D3 in quarterly distributions of the Vitamin D External Quality Assessment Scheme (DEQAS). Based on the agreement of the CDC method with the NIST RMP, the CDC-assigned DEQAS values for 24,25(OH)2D3 may offer a better accuracy basis than the current participant consensus values.

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Keywords

Standards, Reference materials, Health, Clinical diagnostics, Chemistry and Analytical chemistry

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