Evaluation of four automated clinical analyzers for the determination of total 25(OH)D in comparison to a certified LC-MS/MS

Objectives: The aim of this study was to compare the results of five methods for the determination of total 25(OH)D. For that purpose, two mass spectrometry and three immunoassay methods were used. Methods: A total of 124 serum samples were analyzed on five different methods (i.e., a reference LC-MS/MS, Cascadion, Lumipulse, Roche Elecsys II and Roche Elecsys III). Analytical performance against LC-MS/MS was evaluated and compared to the Milan models 1 (analytical performance based on the clinical outcome using thresholds of 12, 20 and 30 ng/mL) and 2 (analytical performance based on biological variation). Additionally, imprecision studies and accuracy using NIST SRM972a samples were carried out. Results: Compared to the reference LC-MS/MS method, the Lumipulse and the Roche Elecsys III assays reached the optimal criterion for bias, while the Cascadion met the desirable one. The Roche Elecsys II was not able to reach the minimal criteria. The proportion of correctly classified patients was higher using the Cascadion (95.2%) compared to the three immunoassays. In addition to its better precision, the Cascadion was not impacted by a high concentration of 3-epi-25(OH)D3 compared to the three immunoassays. Conclusions: Compared to the LC-MS/MS reference method, the Cascadion presented the highest level of concordance at medical decision cut-offs for total 25(OH)D and reached the desirable specification for bias. Moreover, the presence of 3-epi-25(OH)D3 in enriched samples was only problematic in immunoassay methods, and especially considering Roche Elecsys methods. The release of performant fully automated mass spectrometry assays with high throughput might therefore facilitate the wide scale adoption of LC-MS/MS, even in non-specialized clinical laboratories.