Measurement of Serum Total Vitamin D (25-OH) Using Automated Immunoassay in Comparision With Liquid Chromatography Tandem-Mass Spectrometry

Background The associations of vitamin D deficiency with many nonskeletal diseases are still being discovered. We evaluated the use of an automated immunoassay to measure serum total vitamin D (25‐OH) and assessed vitamin D status in a Korean adult population. Methods We compared the Elecsys Vitamin D (25‐OH) Total Assay (Roche Diagnostics) with liquid chromatography‐tandem mass spectrometry (LC‐MS/MS) using 300 serum samples. Total imprecision was calculated using three levels of quality control materials and serum samples. We also investigated the vitamin D status using data for 70,762 cases who had a routine health check‐up in our hospitals. Results The regression equation: Elecsys = 0.882 × LC‐MS/MS + 6.814 (r = 0.926). Total imprecision was within 10% for all quality control materials and serum samples. The prevalence of vitamin D deficiency using cut‐off values of