A High Throughput Universal Vitamin D Assay for Automated Chemistry Analyzers

A growing body of scientific literature has been showing the importance of measuring the serum levels of 25-OH Vitamin D (considered to be a reliable indicator of the overall Vitamin D status of a patient). Since the development of the first immuno-assays for 25-OH Vitamin D (over four decades ago), significant improvements have been made in the way 25-OH Vitamin D serum levels are measured. These improvements are, however, still lagging when compared to the exponential demand for Vitamin D testing in clinical settings. Indeed, current 25-OH Vitamin D assays are still slow, have low throughput and are still performed by a limited number of clinical laboratories. In this article, we report on a rapid technique to measure serum 25-OH Vitamin D that uses only two reagents and that can be adapted to virtually any automated spectrophotometric chemistry analyzer. The new technique uses polystyrene (latex) nanoparticles that have been sensitized with Vitamin D-specific antibodies. Extensive performance testing of this new 25-OH Vitamin D assay (namely the Diazyme EZ Vitamin D Assay) has been performed on one of the most common clinical chemistry analyzer (the Beckman AU680). Results show that the assay is sensitive, precise, linear, accurate and fast (throughput over 600 tests per hour). The assay has received approval for clinical use by the US Food and Drug Administration (FDA) and is certified (for accuracy and precision) by the Center for Disease Control and Prevention (CDC).