Technical Points in Vitamin D Measurement Assays

Background and aim: Major sources for vitamin D (Vit D3& Vit D2) in humans are skin and diet. Vitamin D is needed to maintain calcium concentrations within a narrow physiologic range and its status is assessed by measuring total serum levels of 25-hydroxyvitamin D, 25(OH) D metabolite. Despite the availability of many methods including High Performance Liquid Chromatography (HPLC), Liquid Chromatography -Mass Spectrometry (LC-MS/MS) and different immunoassays, the sensitivities and specifications of these vary considerably.Methods: For the present paper, electronic databases including; PubMed, Scopus, Scientific Information Database, and etc during years 2000 to 2019 were selected and related papers were reviewed.Results: The investigations indicated significant laboratory variation on the values generated for the 25(OH) D metabolite measurement in the same specimen using different methods and assays.Conclusion: In summary, the choice to which assay or method to use for routine serum vitamin D determination will depend on the available equipment and expertise of each laboratory. In addition, to the contribution of different international programs for vitamin D metabolites measurement- to minimize inter assay and intra assay laboratory variations- it is suggested to use a suitable commercial serum control materials along with the manufacture’s quality control material for vitamin D routine determinations. So that each laboratory can establish its own assay specific clinical decision limits based on the institute of medicine recommendations for low and upper safe limits of vitamin D.