[Estimation of 25-hydroxyvitamin D in blood serum using competitive binding with protein]

A modified procedure is described for estimation of 25-hydroxyvitamin D (25OHD) in blood serum, which involves a principle of the saturating analysis. Blood serum from rats, maintained on a ration free of vitamin D, was used as a binding system. Evaluation of the procedure was carried out by conventional criteria (accuracy, reproducibility, sensitivity). Content of 25OHD was estimated in blood of rats, maintained on rations containing various amount of vitamin D, as well as in blood of women in childbirth and in newborns from different climatogeographical zones.