“…Radioisotopic assays for folate measurement have been explored since folate binders were identified in milk (Ghitis, 1967) and in animal (especially porcine) sera (Mantzos et al, 1974). A variety of methods have been documented (Waxman et al, 1971;Rothenberg et al, 1972;Dunn and Foster, 1973;Mantzos, 1975) recently, all of which suffer from the shortcomings of scintillation counting associated with the use of tritiated folic acid, which appears to prohibit their widespread application for clinical diagnostic purposes (Coulson and Rose, 1974;International Society of Haematology, London, 1975). Further development of a method, using a gamma-emitting radiofolate adhering to basic principles of saturation analysis, has yielded a simple, reliable, and effective method which has a number of advantages compared with the L. casei assay.…”