Evaluation of the analytical performance of the Beckman Coulter Unicel DXI 800 Access Total 25(OH) Vitamin D immunoassay

As vitamin D has recently been implicated in various diseases, vitamin D testing has gained a lot more significance. Vitamin D deficiency is quite prevalent, and detection of this condition is important. Several manufacturers have developed new automated immunoassays for this purpose. In this study, we aimed to evaluate the analytical performance of the Access Total 25(OH) Vitamin D immunoassay on the Beckman Coulter Unicel DXI 800 analyzer, through comparison with the reference method, liquid chromatography/tandem mass spectrometry (LC-MS/MS).Methods The study was conducted with 148 patient samples which were sent to Ankara Numune Training and Research Hospital for routine vitamin D testing. Every sample was analyzed with both Unicel DXI 800 immunoassay analyzer and LC-MS/MS. The concordance of the results was evaluated with Passing-Bablok regression analysis and Bland-Altman plot. Additionally, imprecision, interference, limit of blank (LOB), recovery, linearity and carry-over studies were performed for the Beckman Coulter Unicel DXI 800 analyzer.Results When compared to LC-MS/MS, the Access Total 25(OH) Vitamin D immunoassay on the Beckman Coulter Unicel DXI 800 analyzer had an R-value of 0.957 (intercept: −3.938, slope: 1.185) and a mean bias of 9.5%. The concordance correlation coefficient (CCC) between the two methods was 0.916. The intra-assay, inter-assay and total coefficient of variation (CV%) for the Unicel DXI 800 vitamin D immunoassay were 3.3%, 5.3% and 8.3%, respectively, at 31.7 ng/mL concentration, and 2.1%, 3.2% and 7%, respectively, at 66.8 ng/mL concentration.Conclusions The Access Total 25(OH) Vitamin D immunoassay method has acceptable analytical performance, and the results are in concordance with the LC-MS/MS results.