Background: Vitamin D deficiency is considered a major health issue and therefore there is a need for reliable routine tests for measurement of the vitamin in blood samples. Here we present a validation of the recently released Roche 25-OH Vitamin D Total assay (Vitamin D Total). Methods: We analyzed control materials (2 levels) and patient serum pools (3 levels) ranging from 34 to 123 nmol/L 84 times over a period of 21 days, and we analyzed five serum pools in 10 separate runs to verify the limit of quantification. We also analyzed 53 paired samples of serum and Li-heparin plasma. We evaluated the 25-OH Vitamin D Total assay in comparison to our in-house liquid chromatography tandem mass spectrometry (LC-MS/MS) method [194 patient samples without 25-hydroxy vitamin D2 (25OHD2) and 23 patient samples containing 25OHD2]. Results: At concentrations of 34 and 56 nmol/L within-run CVs were 4.8% and 1.9% and total CVs were 8.3% and 6.1%. We verified that the limit of quantification was 22.5 nmol/L, as stated by the manufacturer. No significant difference was observed between serum and plasma samples (Li-heparin). Comparison with LC-MS/MS using 194 samples containing 25OHD3 only (no 25OHD2) showed Vitamin D Total nmol/L=1.07×(LC-MS/MS) nmol/L+4.7 nmol/L, whereas comparison of 25OHD2 using 23 patient samples showed Vitamin D Total nmol/L=0.55×(LC-MS/MS) nmol/L–2.38 nmol/L (Demings regression). Conclusions: The Roche Vitamin D Total assay is judged suitable for measurement of 25OHD in serum and Li-heparin plasma. Results for 25OHD3 are comparable to those obtained by LC-MS/MS, while results for 25OHD2 are around half of those obtained by LC-MS/MS.
Clinical Chemistry and Laboratory Medicine, 2012, Vol 50, Issue 11, p. 1965-8