Approaches to measurement of Vitamin D concentrations - Immunoassays

Abstract

The clinical relevance of vitamin D calls for analytically reliable and cost-effective testing methods. 25-hydroxyvitamin D (25(OH)D), the storage form of vitamin D in the blood circulation, is widely accepted as the best indicator of the individual vitamin D status. 25(OH)D immunoassays play a major role in routine testing in the clinical laboratory and many new automated immunoassays have been introduced to the market by the diagnostic industry in recent years. Detectability, precision, traceability and comparability to the reference method liquid chromatography – tandem mass spectroscopy (LCTMS) are essential quality requirements for 25(OH)D immunoassays. The hydrophobic nature of the analyte, the high concentration and affinity of vitamin D binding protein (VDBP) in serum and the cross-reactivity requirements due to the broad spectrum of metabolites of vitamin D are most demanding for assay development. It requires an adequate assay design including a thorough pretreatment process to inactivate the VDBP, careful selection of the specifier (antibody or binding protein) to meet the cross-reactivity requirement, and standardization of the assay versus LCTMS to achieve comparability of results between methods.

Key Words::

• 25-Hydroxyvitamin D
• Vitamin D binding protein
• VDBP

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ERRATA

Declaration of interest: The author report no conflicts of interest. The author alone is responsible for the content and writing of the paper.