Histidine Metabolic Loading Test to Distinguish Folic Acid Deficiency From Vit. B 12 in Megaloblastic Anemias. ∗ †

Abstract

Summary

1) A new procedure for diagnosis of clinical folic acid deficiency is described which distinguishes it from Vit. B₁₂ deficiency. This permits differentiation of Addisonian pernicious anemia in relapse from megaloblastic anemia due to folic acid deficiency. 2) The procedure is based upon oral administration of 15 g of L-histidine monohydrochloride for 48–72 hours and measurement of urinary concentration or 24-hour excretion of formiminoglutamic acid, which accumulates in folic acid deficiency. Under these conditions, urine FIGLU levels do not exceed 30 γ/ml in non-folic acid deficient individuals; are 3 to 1000 fold greater in folic acid deficiency.