Diagnostic Value of Small Oral Doses of Folic Acid in Megaloblastic Anaemia.

The introduction of reliable techniques for the measurement of serum levels of vitamin B12 and folate has meant that megaloblastic anaemias can be more readily classified as being due to deficiency of one or occasionally both of these substances. The excretion of formiminoglutamic acid (figlu) in the urine of patients with folic-acid deficiency has further aided this differentiation. However, unless these tests clearly indicate deficiency of one substance with normal levels of the other, differentiation is often not precise. It has been shown that in vitamin-B12 deficiency serum-folate levels can be low, normal, or raised (Hansen and Weinfeld, 1962), and in folic-acid deficiency the vitamin-B12 level may be normal or reduced (Johnson et al., 1962. Figlu excretion may also occur in patients with vitaminB12 deficiency (Chanarin et al., 1962). There would therefore seem to be a place for the use of a therapeutic trial of vitamin B12 or folic acid as a further aid in the differentiation of megaloblastic anaemia provided a " physiological" dosage is given. Oral administration of folic acid in small doses would appear to be the easiest way of attempting such an investigation. Folic-acid deficiency, apart from that occurring in the malabsorption syndrome, has been infrequently recognized in the past, and a significant response to small doses of folic acid would provide good evidence of such a deficiency. Reports of the value of small doses of folic acid in the differentiation of the cause of megaloblastic anaemia have appeared in the literature (Marshall and Jandl, 1960; Hansen and Weinfeld, 1962), but the methods and dosages employed have varied, so that a standard procedure has not been established. This paper describes the effect of the administration of small (200 [kg. daily) oral doses of folic acid in a group of patients with megaloblastic anaemia.