Traditional reference values for serum vitamin B12 and folate are not applicable to automated serum vitamin B12 and folate assays: comparison of value from three automated serum vitamin B12 and folate assays

「Summary」Because dietary reference intakes of vitamin B12 and folate are set based on the amount needed for the maintenance of serum concentrations of these vitamins above a lower reference value (200 pg/mL for vitamin B12 and 3 ng/mL for folate by microbiologic assays), we investigated whether these values are applicable to automated competitive protein binding (CPB) assays. In serum specimens collected from volunteers, vitamin B12 and folate were determined by three automated CPB methods, i.e., Access, Advia Centaur and Elecsys. Observed values of serum folate and vitamin B12 were significantly correlated among each method. There is a significant difference in mean folate concentrations in serum among the biologic assay and the three automated CPB methods, and the values of vitamin B12 by Elecsys and those of folate by Advia Centaur were significantly higher. Because the bias around 200 pg/mL for vitamin B12 and 3 ng/mL for folate was too large to directly compare observed values by each method, traditional reference values for serum vitamin B12 and folate are not applicable to automated CPB methods.