Vitamin D Standardization Program (VDSP)

The Vitamin D Standardization Program (VDSP) was begun to correct widespread variation in 25‐hydroxyvitamin D [25(OH)D] lab results that confounds international efforts to develop evidence‐based clinical & public health guidelines. Its objectives are to: (1) standardize measurement of total 25(OH)D in national health surveys world‐wide by linking them to the NIST reference measurement procedure (RMP); (2) study differences in 25(OH)D among those surveys; & (3) expand standardization services to include assay manufacturers & clinical & research labs. Measurands addressed in the VDSP are total 25(OH)D, 25(OH)D 2 , 25(OH)D 3 & 3‐epi‐25(OH)D 3. A formal laboratory standardization program will be implemented using procedures similar to those used in CDC Hormone Standardization (HoSt) Program. ODS provides overall coordination. A VDSP Coordinating Center has been established at CDC. NIST and Gent University (Dr. Thienpont), Belgium are the reference labs for the VDSP. Currently, VDSP is conducting an inter‐laboratory comparison study that includes labs from eight national surveys (Australia, Canada, Germany, Ireland, Mexico, South Korea, UK & US) as well as research labs & assay manufacturers to assess measurement variability in currently used assays. Data from this study will be used to create master equations to facilitate the conversion of already existing data from national health surveys to the NIST RMP.