Semiautomated system for simultaneous assays of serum vitamin B12 and folic acid in serum evaluated.

We evaluated performance characteristics of a semiautomated radioassay system (ARIA II, Becton Dickinson Immunodiagnostics) for simultaneous measurements of vitamin B12 and folic acid in serum. The system requires off-line boiling of samples, which are then processed on-line. The automated process includes dispensing of boiled samples, tracers, and binders (purified intrinsic factor and milk binder); incubation, separation of bound and free ligands; elution; counting radioactivity of 57Co and 125I; and data reduction. Results were compared with those obtained by a manual method (Diagnostic Products Corp.). Although the nonspecific binding of the ARIA II is more than double that of the manual system, the precision values are comparable (within- and between-assay CVs are less than 8.5%). Values obtained with these two systems correlated well except that folic acid concentrations obtained with ARIA II tended to be lower at high folic acid concentrations. We observed no significant total carryover or drift in the semiautomated system.