Radioassay of serum vitamin B12 using a competitive protein binding technique

A method has been developed for the radiassay of serum vitamin B₁₂ using a competitive binding technique. By this method, vitamin B₁₂ levels as low as 50 pg per ml of serum can be estimated in test samples. Egg yolk has been used as a test binding protein, which has several advantages over serum or plasma protein binding agents, as described in this paper. This binder is quite suitable and reliable for the assay of vitamin B₁₂.