Multicenter Comparison of Seven 25OH Vitamin D Automated Immunoassays

The measurement of 25OH vitamin D continues to grow in clinical laboratories. The aim of this multi-center study was to compare the results of seven automated commercial immunoassays with a reference HPLC technique. One hundred and twenty consecutive outpatient serum samples were centrifuged, divided in aliquots, frozen and shipped to the participating laboratories. 25OH Vitamin D was measured with a reference HPLC system and with seven automated commercial immunoassays (Roche Cobas E601, Beckman Coulter Unicel DXI 800, Ortho Vitros ES, DiaSorin Liaison, Siemens Advia Centaur, Abbott Architect i System and IDS iSYS). Compared to the reference method, the regression coefficients ranged from 0.923 to 0.961 (all p