25-OH-Vitamin D assay variation and subject management in clinical practice

Abstract Objective To compare two methods for assessing vitamin D status in clinical settings. Design and methods 25-OH-vitamin D status was measured in 120 patients by HPLC and a commercial immunoassay. Results Only 53% of the subjects considered as vitamin D sufficient by immunoassay fell within this category according to HPLC although subjects with concentrations above 75 nmol/L, regardless of the method used, presented normal PTH concentrations. Conclusions Both methods are not exchangeable to classify subjects based on unique cut-offs but they are comparable when interpreted in relation with PTH concentrations.