COMPARISON OF 3 COMMERCIAL KITS AND A MICROBIOLOGICAL ASSAY FOR THE DETERMINATION OF VITAMIN-B12 IN SERUM

Different methods are available for cobalamin determination in serum. Microbiological and radio ligand binding assays are the most commonly used. Kits involving non-isotopic competitive-binding assay have been recently commercialized. In the present work, cobalamins were determin ed in 146 patient sera, using four methods: a microbiological method, two no boil radio ligand binding assay kits (Magic B12 FOL (NB) from C iba-Corning and SimulTRAC SNB No Boil from Becton Dickinson) and a non -isotopic kit with acridinium ester labelled cobalamin (Magic Lite fro m Ciba-Corning). Median (range) cobalamin concentrations in pmoll(-1) were 317 (15-1291) using the microbiological method, 355 (25-3469) usi ng the Magic Lite kit, 355 (35-2312) using the Magic B12 FOL (NB) kit and 380 (37-2021) using the SimulTRAC SNB No Boil kit. The ANOVA test indicated that differences between methods were statistically signific ant (p < 0.01). Competitive-binding methods gave higher results than t he microbiological method. Although correlation coefficients were not excellent (0.88 < r < 0.96), the results obtained with the different m ethods were generally similar and confirmed that competitive methods a re useful for detecting low serum concentration of vitamin B-12