Multicenter Evaluation of Current Total 25-OH Vitamin D Assays: A Comparison of the Roche Elecsys Protein Binding Assay and Four Immunoassays With a NIST-Standardized LC-MS/MS Method

The pathophysiologic importance of vitamin D is increasingly recognized.New immunoassays have been developed to meet the needs of the increasing test volume.High variability between 25-OHD assays has been reported.We compared performance of the Elecsys Vitamin D Assay (Roche Diagnostics, Indianapolis, IN) and 4 immunoassays (Architect (Abbott Diagnostics, Lake Forest, IL), Centaur (Siemens, Malvern, PA), Liaison/Liaison XL (DiaSorin, Stillwater, MN) and IDS-iSYS (IDS Inc, Scottsdale, AZ)) with a NIST-standardized LC-MS/MS, across four US laboratories.Precision performance was evaluated (3 replicates of 5 samples; ranging from 10-50 ng/mL; 2 runs/day for 5 days).Elecsys, IDS-iSYS and Architect showed good repeatability and within site/lot precision (CV<8%, 20-50ng/mL); CV was <17.5% for Centaur and <14% for Liaison assays.Samples from routine vitamin D testing (cohort I, n=300), predialysis patients (cohort II, n = 50), pregnant women (cohort III, n = 50), and intensive care patients (cohort IV, n = 50) were measured for 25-OHD.Deming regression analysis comparing commercial assays and LC-MS/MS measurements was performed.In cohort I and cohort II-IV, regression parameters versus LC-MS/MS ranged 0.93-1.26and 0.86-1.61for slope; 0.77-0.91 and 0.79-0.93 for Pearson's r, respectively.Highest slopes were seen generally with IDS-iSYS and Centaur.Highest correlation coefficients were generated by Elecsys, Liaison XL, and IDS-iSYS.Vitamin D sufficiency prevalence was calculated for all cohorts combined.Using 20 ng/mL as cutoff, vitamin D sufficiency prevalence was 67.6% for LC-MS/MS versus 66.0%, 67.3%, 70.4%, 65.6% and 66.4% for Elecsys, Architect, Centaur, Liaison, and Liaison XL.Using 30 ng/mL as cutoff, vitamin D sufficiency prevalence was 38.9% for LC-MS/MS versus 40.0%, 34.4%, 42.9%, 33.8%, and 38.7% for other assays, respectively.Although variability was observed among all assays versus LC-MS/MS, comparable vitamin D sufficiency prevalence was observed.The Elecsys protein-binding assay demonstrated good precision and correlation to LC-MS/MS and is suitable for routine total vitamin D determination.