A Clinical Evaluation of a Rapid Method for Determination of Folate Deficiency by14C-Formate Incorporation into Serine of Lymphocytes

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Abstract
A rapid modification of a previously described method (3), for the determination of folate activity from the rate of incorporation of 14C-formate into serine of lymphocytes (the C1-index) is presented. The C1-index of a control group averaged 1.34 ± 0.09 (S.E.M.) nmol per 108 lymphocytes per h (n=16). The range of observed values, 0.94–2.10 nmol, is taken as the normal range. In a material of 41 patients who were not suspected of folate deficiency, the C1-index was compared to other parameters of folate deficiency. A statistically significant correlation was only found between a subnormal C1-index and the combined presence of an increased excretion of formiminoglutamic acid (> 20 μmol/h) and a subnormal erythrocyte folate concentration (< 90 ng/ml). A group of patients presenting a history of poor folate intake also had decreased C1-index.