Experience with a commercial kit for the radioisotopic assay of vitamin B12 in serum: the Phadebas B12 test.

The first commercial kit for the radioisotopic assay of vitamin B(12) in serum-the Phadebas B(12) Test produced higher values than the radioisotopic method of Raven, Robson, Walker, and Barkham (1969) and the Lactobacillus leichmannii microbiological assay. Its normal range was 300-1100 pg/ml and its reproducibility was similar to that of the other radioisotopic method. It should be possible to lower the results obtained by the Phadebas method by modifying its standard curve and to reduce the time taken for the assay by shortening its incubation period.