RADIOISOTOPIC ASSAYS OF VITAMINE B12 - IN TEREST OF KAPPA INDEX IN A MULTICENTRIC STUDY

Owing to the lack of a reference tedhnique and of an international cob alamin (vitamin B12) standard, and the large discrepancy between labor atory norms, the authors performed a multicentric study to compare fiv e RIA kits usually used. First, classical tests were used to evaluate the analytical performances of each kit. Results did not demonstrate a ny superiority of one kit over another. Secondly, B12 values were clas sified among three categories (low, normal and high) caracterized by l aboratory and then manufacturer norms. The concordance between these t wo ''judgments'' was evaluated with the Kappa coefficient. In addition , the Kappa index proved that the norms supplied by the manufacturer w ere better than those of laboratories. But mean Kappa coefficient esta blished for each norm gave us an insatisfactory result. Third, clinica l informations allowed to improve the classification of the patients. New limits were defined for each technique and should be tested furthe r, routinely in each laboratory.