Detection bias evaluation of ten commercial total 25-hydroxyvitamin D immunoassays

Obejective To evaluate the accuracies of ten commercial total 25-hydroxyvitamin D[25(OH)D]immnoassays. Methods NIST 25(OH)D reference material SRM 972a, which consisted of four vials of frozen serum with different concentration levels of different 25(OH)D types, and two human serumsamples provided by our lab(BIMT), which had different concentration levels of 25(OH)D3,were analyzed by ten total 25-hydroxyvitamin D immnoassays from Biomerieux, Mindray, Maccura, Chemclin, Abbott(2), Siemens, SNIBE(2), Roche, and by isotope-dilution liquid chromatography-tandem mass spectrometry(ID-LC/MS/MS) founded by BIMT. For the measurements of SRM 972a, the biases between tested values and certified values were calculated as a evaluating indicator, meanwhile the test biases between immnoassays and ID-LC/MS/MS were used as a evaluating indicator for the measurements of BIMT 25(OH)D3 serum samples. Test bias lower than 10% was deemed acceptible. Results The ID-LC/MS/MS exhibited low biases at (1.6%-2.8%) in the measurements of all levels of SRM 972a. 8 immnoassays showed low biases at(1.5%-3.5%)in the measurements of level 1 of SRM 972a, which had a high 25(OH)D3 concentration level, but only 2 immnoassays gave low biases at(3.6%-3.7%)in the measurements of high 25(OH)D2 concentration sample(level 3). While, 5 immnoassays gave low biases at(-0.3%-9.0%)in the measurements of high 3-epi-25(OH)D3 concentrationsample (level 4). It seems that, when SRM 972a were analyzed, only one of the ten commercial total 25(OH)D immnoassays were in good accuracy and analytical specificity agrements with ID-LC/MS/MS. When two human serum25(OH)D3 samples from BIMT were tested, most immunoassays were overall in relative good agreement with ID-LC/MS/MS at high 25(OH)D3concentration level. Conclusion The test biases in the total 25(OH)D measurements are differences between differentimmnoassays and ID-LC/MS/MS, and the specificities of current commercial total 25(OH)D immnoassays should be improved, especially the performance on the equivalent recognition of 25(OH)D2 and 25(OH)D3.(Chin J Lab Med, 2017, 40: 320-325) Key words: 25-hydroxyvitamin D2; Calcifediol; Immunoassay; Indicator dilution techniques; Isotopes; Chromatography, liquid; Uncertainty