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Open Access General Steps to Standardize the Laboratory Measurement of Serum Total 25-Hydroxyvitamin D

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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 the traceability of 25-hydroxyvitamin D [25(OH)D] assays to relevant reference measurement procedures and reference materials. This is done with the goal of verifying end-user laboratory performance using precise statistical criteria to determine whether a specific assay is standardized. The purpose of this paper was to outline a set of steps that routine clinical and research laboratories can use to standardize their 25(OH)D assays using these tools. These steps apply to laboratories using commercially developed immunoassay measurement systems as well as in-house assays, usually based on high HPLC or LC tandem MS measurement systems. The steps are (1) initial calibration, (2) initial assessment of accuracy and bias, (3) assessment of total percent CV and mean bias, (4) use of trueness controls, and (5) participation in accuracy-based performance testing and/or external quality assessment schemes. The goal of each laboratory assay is to have a total CV of ≤10% and mean bias of ≤5%. Rigorous and less rigorous but low-cost options for meeting these statistical criteria are provided. Research laboratories who infrequently measure 25(OH)D are advised to repeat steps 1–4 for every measurement cycle. For users of commercial immunoassays who have relatively little control over standardization, we present an option for using trueness controls to develop a master equation that can be used to standardize results to the reference methods.

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Document Type: Editorial

Affiliations: 1: National Institutes of Health, Office of Dietary Supplements, Bethesda, MD 2: National Institute of Standards and Technology, Chemical Sciences Division, Gaithersburg, MD 3: Imperial College Healthcare NHS Trust, London, United Kingdom 4: University of Liège, Centre Hospitalier Universitaire de Liège, Department of Clinical Chemistry, Liège, Belgium 5: The University of Western Australia, Centre for Microscopy, Characterisation and Analysis, Perth, WA, 6009 Australia 6: University College Cork, School of Food and Nutritional Sciences, Cork Centre for Vitamin D and Nutrition Research, Cork, Ireland 7: Loyola University Chicago, Department of Public Health Sciences, Chicago, IL 8: University of Washington, Department of Laboratory Medicine, Seattle, WA 9: Sonic Healthcare, Douglass Hanly Moir Pathology, Sydney, NSW, Australia 10: National Institute of Standards and Technology, Biomolecular Measurement Division, Gaithersburg, MD 11: Health Canada, Nutrition Research Division, Ottawa, ON, Canada

Publication date: 01 September 2017

This article was made available online on 01 August 2017 as a Fast Track article with title: "General Steps to Standardize the Laboratory Measurement of Serum Total 25-Hydroxyvitamin D".

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  • The Journal of AOAC INTERNATIONAL publishes refereed papers and reviews in the fields of chemical, biological and toxicological analytical chemistry for the purpose of showcasing the most precise, accurate and sensitive methods for analysis of foods, food additives, supplements and contaminants, cosmetics, drugs, toxins, hazardous substances, pesticides, feeds, fertilizers and the environment available at that point in time. The scope of the Journal includes unpublished original research describing new analytical methods, techniques and applications; improved approaches to sampling, both in the field and the laboratory; better methods of preparing samples for analysis; collaborative studies substantiating the performance of a given method; statistical techniques for evaluating data. The Journal will also publish other articles of general interest to its audience, e.g., technical communications; cautionary notes; comments on techniques, apparatus, and reagents.
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