Vitamin D assays in clinical laboratory: Past, present and future challenges.

Vitamin D status is usually assessed by measuring the serum 25-hydroxyvitamin D (25(OH)D) concentration. There has been a dramatic increase in 25-OHD requests over recent years prompting many laboratories to consider the use of automated immunoassays. In this presentation, we will discuss and compare the two major techniques that are used for measuring of vitamin D (the binding assay and chemical assay techniques). Chemiluminescence immunoassays (CLIA), radioimmunoassy (RIA), and binding protein assay are belonging to the binding assay, while the chemical assay includes high performance liquid chromatography (HPLC) and liquid chromatography-tandem mass spectrometry (LC-MS/MS). Significant differences in the 25(OH)D determination were observed between various assays. Standardization and harmonization of 25(OH)D measurements are therefore urgently needed. The widespread introduction of well standardized assays in clinical laboratories is the challenge in the next years.