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General steps to standardize the laboratory measurement of serum total 25-hydroxyvitamin D



Karen W. Phinney, Christopher T. Sempos, J. M. Betz, Johanna Camara, Graham D. Carter, E. Cavalier, Michael W. Clarke, Kirsten D. Dowling, Ramon Durazo-Arvizu, Andrew N. Hoofnagle, A Liu, Kurtis Sarafin, Stephen A. Wise, Paul M. Coates


The Vitamin D Standardization Program (VDSP) has collaborated with numerous groups and agencies to assemble a set of tools, i.e. a reference measurement system, that can be used to establish traceability of 25-hydroxyvitamin D [25(OH)D] assays to relevant reference measurement procedures and reference materials. This is done with the goal to verify end-user laboratory performance using precise statistical criteria to determine if a specific assay is standardized. The purpose of this paper is to outline a set of steps that routine clinical and research laboratories can use to standardize their 25(OH)D assays using those tools. The steps apply to laboratories using commercially developed immunoassay measurement systems as well as in-house assays which are usually high performance liquid chromatography (HPLC) or liquid chromatography tandem mass spectrometry (LC-MS/MS) measurement systems. The steps are: (1) Initial calibration; (2) Initial assessment of accuracy and bias; (3) Assessment of total coefficient of variation (CV%) and mean bias (%); (4) Use of trueness controls; and (5) Participation in accuracy-based performance testing/external quality assessment schemes. The goal of each laboratory assay is to have a total CV ≤ 10% and mean Bias ≤ 5%. Rigorous and less rigorous but low-cost options for meeting those statistical criteria are provided. Research laboratories who measure 25(OH)D infrequently are advised to repeat Steps 1-4 every measurement cycle. As users of commercial immunoassays have relatively little control over the assays an option for using trueness control results to develop a master equation that can be used to standardize results to the reference methods and materials is presented.
Journal of Aoac International


Standard Reference Material, high performance liquid chromatography, liquid chromatography – tandem mass spectrometry, immunoassay, reference measurement procedure, total 25-hydroxyvitamin D, Vitamin D Standardization Program, VDSP


Phinney, K. , Sempos, C. , Betz, J. , Camara, J. , Carter, G. , Cavalier, E. , Clarke, M. , Dowling, K. , Durazo-Arvizu, R. , Hoofnagle, A. , Liu, A. , Sarafin, K. , Wise, S. and Coates, P. (2017), General steps to standardize the laboratory measurement of serum total 25-hydroxyvitamin D, Journal of Aoac International, [online], (Accessed July 25, 2024)


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Created August 1, 2017, Updated June 2, 2021