Critical evaluation of assays for vitamin D status

The objective is to highlight new aspects and methodological developments in the assessment of vitamin D status in clinical settings.

Recent advances in the assessment of vitamin D status mostly concern two areas: the emerging clinical and analytical interest in other circulating vitamin D metabolites [i.e. 3-epimer and 24,25-(OH)2 D] that opens a new perspective for the vitamin D metabolite profiling in health and disease and methodological improvements including the development of reference measurement procedures, the certification of Standard Reference Materials, the development and application of Standardization protocols and the change of the Vitamin D External Quality Assurance Survey (DEQAS) to an accuracy-based proficiency testing scheme.

Despite the improvement in the analytical imprecision between methods and laboratories over the last years, the reported prevalence of vitamin D deficiency in a given population still depends on the method used. Improvements in quality control procedures, however, will improve the standardization, accuracy and comparability of methods. At present, the analytical evaluation of other circulating vitamin D metabolites (vitamin D profiling) and their clinical utility is, however, limited to liquid chromatography users.