Technical and clinical evaluation of the VITROS Immunodiagnostic Products 25-OH Vitamin D Total Assay - comparison with marketed automated immunoassays and a liquid chromatography - tandem mass spectrometry method

Background: The study was conducted to evaluate the technical and clinical performance of the VITROS ® Immunodiagnostic Products 25-OH Vitamin D Total Assay, and compare it with the performance of five marketed automated assays and a liquid chromatography/mass spectrometry reference method (LC-MS/MS).
Methods: Three hundred patient serum samples were used to compare the correlation of the VITROS ® 25-OH Vitamin D Total Assay with both the other immunoassays and the LC-MS/MS method, using Passing-Bablok regression and Bland-Altman analyses. Concordance of the diagnosis of vitamin D status was calculated to test the agreement between the different assays. In addition, samples containing vitamin D2 were used to test the assay ’ s ability to detect the D2 form of the vitamin.
Results and conclusions: These results from the VITROS ® 5-OH Vitamin D Total Assay generally correlated well with those from most of the marketed immunoassays. Cross-reactivity of the D2 form was calculated as being close to 100%. Additionally, we found substantial variability in performance amongst the various assays, which suggests the need for optimisation and recalibration of commercial methods.