Development of a standard reference material for vitamin D in serum.

The most widely used indicator of vitamin D status is the measurement of 25-hydroxyvitamin D [25(OH)D] in either serum or plasma. Several studies have reported discrepancies between the results of assays used to measure 25(OH)D, however, which calls into question the ability of 25(OH)D assays to reflect accurately the vitamin D status of individuals. The National Institute of Standards and Technology has been working with the National Institutes of Health's Office of Dietary Supplements to develop a standard reference material for circulating vitamin D analysis. This standard reference material will provide a material with stable, well-defined levels of the analytes of interest. Investigators will be able to use the standard reference material to validate new analytic methods as they are developed and to assign values to in-house quality-control materials.