Commercially-supplied binders for plasma cobalamin (vitamin B12), analysis--"purified" intrinsic factor, "cobinamide"-blocked R-protein binder, and non-purified intrinsic factor-R-protein binder--compared to microbiological assay.
Recent evidence (Kolhouse et al., N. Engl. J. Med. 299: 785-792, 1978) demonstrates that commercial cobalamin (Vitamin B12) radioassay kits contain nonspecific R-protein binding agents that can give falsely normal results in patients who are actually cobalamin deficient. We tested three kits: with "purified" intrinsic factor as the binder, with intrinsic factor and the nonspecific R-protein sites blocked with "cobinamide," and non-purified intrinsic factor-R-protein binder. Results with use of the first two compared well with those by a microbiological assay (Lactobacillus leichmannii) and are in harmony with clinical impressions.
D001681:Biological Assay; D002352:Carrier Proteins / Q000097:blood*; D003038:Cobamides; D006801:Humans; D007437:Intrinsic Factor / Q000097:blood*; D007778:Lactobacillus; D011863:Radioimmunoassay; D011933:Reagent Kits, Diagnostic; D014155:Transcobalamins / Q000097:blood*
D002352:Carrier Proteins; D003038:Cobamides; D011933:Reagent Kits, Diagnostic; D014155:Transcobalamins; C017142:cobinamide; D007437:Intrinsic Factor