A rapid point-of-care assay accurately measures vitamin D

Albrecht, K.; Lotz, J.; Frommer, L.; Lackner, K. J.; Kahaly, G. J.

PURPOSE: Vitamin D (VitD) is a pleiotropic hormone with effects on a multitude of systems and metabolic pathways. Consequently, the relevance of a sufficiently high VitD serum level becomes self-evident. METHODS: A rapid immunofluorescence assay designed for the point-of-care measurement of serum VitD(3) solely was tested. Inter- and intra-assay validation, double testing and result comparison with a standardized laboratory method were performed. RESULTS: An overall linear correlation of r = 0.89 (Pearson, 95% CI 0.88–0.92, p < 0.01) between the point of care and the conventional reference assay was registered. Accuracy and precision were of special interest at cut-points (10 ng/ml [mean deviation 1.7 ng/ml, SD 1.98 ng/ml, SE 0.16 ng/ml], 12 ng/ml [MD 0.41, SD 1.89, SE 0.19] and 30 ng/ml [MD − 1.11, SD 3.89, SE 0.35]). Only a slight deviation was detected between the two assays when using fresh (r = 0.91, 95% CI 0.86–0.94, p < 0.01) and frozen serum samples (r = 0.86, 0.82–0.89, p < 0.01). Results remained steady when samples were frozen several times. Inter- and intra-assay validation according to the CLSI protocol as well as multiuser testing showed stable results. CONCLUSION: This novel, innovative, and controlled study indicates that the evaluated rapid point of care VitD assay is reliable, accurate, and suited for clinical practice.