The new Roche Vitamin D Total assay: fit for its purpose ?

Background: Measurement of serum 25-hydroxyvitamin D [25(OH)D] is used to assess vitamin D status. We evaluated the analytical performance of a new automated assay, Elecsys Vitamin D Total (Roche Diagnostics, Mannheim, Germany), based on competitive protein binding. Methods: The Elecsys assay was tested for imprecision, linearity and functional sensitivity at three test-sites and compared to a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method, a high-performance liquid chromatography (HPLC) method and the Liaison 25(OH) Vitamin D Total immunoassay (Diasorin). Results: Imprecision testing with human serum specimens showed within-run CVs of <= 6% and between-run CVs of <= 8%. The assay was linear from 33 up to at least 111 nmol/L and showed equivalent 25(OH) D levels for matched serum and heparinized plasma samples. The assay correlated reasonable to well with LC-MS/MS (r=0.93; y=1.07x-5.04 nmol/L), HPLC (r=0.91, y=0.90x+3.03 nmol/L) and the Liaison assay (r=0.86, y=1.19x+2.80 nmol/L). Some of the samples showed large between-method differences. Conclusions: The new Elecsys assay fulfilled present analytical performance requirements and showed close agreement to other well-established methods for 25(OH) D analysis, making it fit for routine assessment of vitamin D status.