A selective and simplified radioimmunoassay of 25-hydroxyvitamin D₃

Abstract

A simple, non-chromatographic and selective assay for determination of 250HD₃ in serum is described. The serum sample is deproteinated with acetonitrile and the supernatant purified over a small prepacked cartridge, Seppak. In the eluate from the cartridge, 250HD₃ is measured by radioimmunoassay. The selectivity of the assay for 250HD₃ is improved by adding vitamin D₂ to the antiserum; the assay is thus capable of measuring 250HD₃ in serum samples containing up to a ratio of 250HD₂/250HD₃ equal to 150. The simplicity, speed and the small amount of sample needed (0.5 ml) make this method suitable for use in a routine clinical laboratory. Because of its selectivity for 250HD₃ the assay is a necessary prerequisite in the further investigation of metabolic discrimination between vitamins D₂ and D₃.

Key Words:

• antiserum
• hormone
• vitamin D₃