Serum folate levels. Comparison of microbiologic assay and radioisotope kit methods

Serum folate levels were measured prospectively in 72 patients and six normal controls using the Lactobacillus casei microbiologic method and a commercially available sequential-binding radioassay kit method. Values between 0 and 14 ng/ml (0 and 31.78 nmol/l) (clinically significant range) obtained by the microbioassay and sequential-binding radioassay were analyzed statistically. The data suggest that comparable values are obtained by the two technics (Y = 0.9 X where Y = radioassay value). Data obtained by the sequential-binding radioassay and a competitive protein-binding radioassay kit were then compared and subjected to statistical analysis. Values obtained by the two radioassay methods were found to be comparable clinically, but significantly different statistically. The authors conclude that these commercially available radioassay kits for measuring serum folate yield reliable values that can be applied to the clinical evaluation of patients with anemia, and can be readily performed in a clinical radioisotope laboratory.