title: The need for a sufficient number of low level sera in comparisons of different serum vitamin B12 assays.
abstract: Eight radiochemical methods for the assay of vitamin B12 in serum were compared with the microbiological assay with Lactobacillus leichmannii ATCC 7830 using 198 individual sera of patients. There was a good agreement between the results of most samples with some kits and the microbiological assay. However, especially in the sera of vitamin B12-deficient patients large discrepancies between the results could occur. These variations were due to both the kits used and the performance of the assays in different laboratories. A sufficient number of non-pooled sera of vitamin B12-deficient patients should be included in investigations to validate radiochemical methods.
mesh_terms: D001681:Biological Assay; D006801:Humans; D007778:Lactobacillus; D008722:Methods; D008832:Microchemistry; D011868:Radioisotopes; D011933:Reagent Kits, Diagnostic / Q000592:standards*; D014805:Vitamin B 12 / Q000097:blood*; D014806:Vitamin B 12 Deficiency / Q000097:blood
chemical_list: D011868:Radioisotopes; D011933:Reagent Kits, Diagnostic; D014805:Vitamin B 12