Estimation of serum folate by a radioassay and a continuous-flow method, compared with an established microbiological tube assay

Serum folate estimates were generally comparable using the three methods, although the 75Se radioassay kit (Radiochemical Centre, Amersham, UK) gave somewhat lower results. Inbatch variations of the manual methods reflected the number of dilution stages. The tube assay and radioassay required similar technician time, but the practical size of a tube assay batch was potentially much larger. The automated method involved less than half the time of the other two methods. The cost per sample using the radio-isotope kit was between 10 and 30 times greater than with the automated technique. (U.K.)