Assay of Serum Vitamin B 12 Concentration Using Co 57 -B 12 and Intrinsic Factor

Abstract

Summary

Based on some observed properties of the B₁₂-I.F. complex, an assay procedure is described for determining serum Vit. B₁₂ levels using isotopically labeled Vit. B₁₂ and intrinsic factor. 83%-112% of crystalline Vit. B₁₂ added to serum was recovered in the assay. Concentrations of Vit. B₁₂ in normal, B₁₂ deficient, and leukemic sera were in the ranges, 104-328 μμg/ml, 0-72 μμg/ml and over 1000 μμg/ml respectively.