A Clinical Evaluation of a Rapid Method for Determination of Folate Deficiency by ¹⁴C-Formate Incorporation into Serine of Lymphocytes

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.

Key Words:

• Folate deficiency
• lymphocytes
• serine synthesis