An Assessment of Automated Vitamin D Measurement Methods Including a Point-of-Care Testing Method, I-CHROMA™ Using the Randox International Quality Assurance Scheme (Riqas)

Abstract

The objective of this review is to firstly assess the performance of commonly used automated Vitamin D measurement methods enrolled in the Randox International Quality Assessment Scheme (RIQAS) against the calculated All Laboratory Trimmed Mean(ALTM), and to secondly evaluate a new point-of-care assay, the Boditech i-CHROMA™ Vitamin D method against the calculated ALTM. The mean estimates of the following vitamin D methods were lower than the ALTM: Abbott Architect, Roche Cobas vitamin D Total, Roche Elecys, Roche Cobas 4000/e411 and Roche Modular, while the mean estimates of the following methods were higher than the ALTM: Siemens Centaur XP/XPT/Classic, Ortho Vitros, and Beckman 600/800.The mean estimates of the following methods were comparable to the ALTM: Diasorin Liaison and IDS SYS. The ALTM of all the automated vitamin D methods in the RIQAS compared very well with all the following methods: Abbott Architect (r2=0.94), Roche Vitamin D Total (r2=0.96), Siemens Centaur XP/XPT/Classic (r2=0.97), Roche Elecys (r2=0.96), Diasorin Liaison (r2=0.84), Roche Cobas 4000/e411 (r2=0.97), IDS SYS (r2=0.86), Roche Modular (r2=0.94) and Beckman 600/800 (r2=0.93) with biases of 4.32, 14.06, -21.62, 14.64, -2.60 and 14.94, -2.18, 12.65 and 1.08nmol/L, respectively. The Ortho Vitro 3600/5600/Eci method correlated very poorly (r2=-0.011). The Beckman 600/800 method had the smallest bias (1.08 nmol/L), followed by the IDS ELISA method with a bias of -2.18nmol/L and the Ortho Vitros method the largest bias. Overall, the laboratory methods with the best combination of a very good correlation (r2> 0.9) and bias (+/- 15% bias difference) with the ALTM were the Beckman 600/800, Abbott Architect, DiaSorin Liaison and IDS ELISA vitamin D methods. The new point of care i-CHROMA™ Boditech Vitamin D method compared well (r2=0.7) with a reasonable bias of -9.97nmol/L compared to the ALTM.