The Use of Radioactive Phosphorus in the Assay of Vitamin D

Abstract

The validity of the radiophosphorus procedure for vitamin D assay reported by Snyder, Eisner and Steenbock has been confirmed. The method has been compared against the line test in concurrent assays and has given potencies agreeing with those obtained with the U.S.P. standard line test. The radiophosphorus assay has been shown to possess several advantages over the U.S.P. “line test.” The prime advantage is that the subjective nature of the line test assay is completely eliminated without any loss in accuracy. Furthermore, complications inherent in the line test, such as calcification evidenced as a diffuse accretion contiguous to the diaphysis, decreased food consumption and insufficient weight gain, do not appear to affect the results when the radiophosphorus method is used.