Evaluation of nonisotopic binding assays for measuring vitamin B12 and folate in serum.

We report the evaluation of the microparticle enzyme immunoassay (MEIA) for estimating vitamin B12 and the ion capture (IC) assay for estimating folate in serum. The assays were performed with the Abbott IMx analyzer. Intra-assay coefficients of variation were from 3.4% to 8.0% for vitamin B12 and from 1.5% to 4.2% for folate, respectively. Interassay coefficients of variation ranged from 6.3% to 8.8% for vitamin B12 and from 3.9% to 11.3% for folate, respectively. Linearity was satisfactory, with an analytical recovery of 119 +/- 4% for vitamin B12 and 95 +/- 8% for folate. The detection limit was 56.2 pmol/l for vitamin B12 and 1.9 nmol/l for folate. Results of these assays correlated well with those from the cloned enzyme donor immunoassay (CEDIA), our current routine method: r = 0.97 for vitamin B12 (n = 47) and r = 0.97 for folate (n = 50). The MEIA and the IC assay were easy to perform with the IMx analyzer.