A multicenter performance evaluation of the new Elecsys Vitamin D total III assay versus reference isotope dilution liquid chromatography tandem mass spectrometry and commercially available comparators

Abstract

Background: Vitamin D deficiency/insufficiency and toxicity are worldwide issues; thus, accurate diagnostic assays are required to measure vitamin D. We evaluated the performance of the new Elecsys® Vitamin D total III assay (Roche Diagnostics International Ltd). Methods: Repeatability and intermediate precision of the Elecsys Vitamin D total III assay (cobas e 601 analyzer) were evaluated at three sites using five human serum pools (HSPs) and two PreciControls (five-day model, one reagent lot [CLSI-EP05-A3]) and compared against prespecified acceptance criteria. A serum verification panel, with reference isotope dilution liquid chromatography tandem mass spectrometry (ID-LC–MS/MS) values, was used for comparator assay/concordance studies at two sites, assessed using unweighted Deming regression. Testing of serum vs. plasma on the Elecsys assay was conducted at one site using samples from healthy adults; assessed using Passing-Bablok regression. Results: Repeatability (HSP1 [16.8–18.4 ng/ml], SD 0.87–1.07; HSP5 [94.5–98.0 ng/ml], CV 1.58%–2.76%) and intermediate precision (HSP1, SD 1.14–1.77; HSP5, CV 2.00%–4.13%) met acceptance criteria across sites. Agreement was observed between the Elecsys assay and (i) the ID-LC–MS/MS verification panel (slope, 0.936–1.01; Pearson's r, 0.960–0.986) and (ii) comparator assays (slope, 0.921–1.15; Pearson's r, 0.958–0.982). The Elecsys assay correctly assigned the highest combined percentage of samples to deficient (100%) and insufficient (89.5%) vitamin D categories vs. comparator assays and demonstrated comparable performance in serum and plasma (y = 0.103 + 0.984x). Conclusions: The Elecsys Vitamin D total III assay demonstrated good analytical performance and compared favorably with other assays, supporting its use in clinical practice.