Applications of the Urinary Tracer Test (of Schilling) as an Index of Vitamin B12 Absorption

Abstract

Twenty-seven patients with pernicious anemia showed an average urinary excretion of 0.5 per cent of an ingested dose of 2 µg of Co60-labeled vitamin B12when tested by the method of Schilling. The ingestion of normal gastric juice increased this to values ranging from 4 to 12 per cent. The intrinsic factor concentrates studied increased the excretion of radioactivity to values ranging up to 7.1 per cent. A net excretion of 2.5 per cent or greater (as measured by the Schilling test) is a good criterion for an expected optimal clinical effect of the intrinsic factor preparation used in patients with pernicious anemia in relapse. Nine of 13 patients with sprue showed an average excretion of 1.1 per cent which was not enhanced by intrinsic factor. This is interpreted as evidence that in some patients there is a deficient absorption of vitamin B12from some cause other than intrinsic factor deficiency. The urinary tracer test was useful in various clinical states to prove or disprove the diagnosis of pernicious anemia. The existence of a group of patients with megaloblastic anemia due to deficient B12absorption, not caused by lack of intrinsic factor and without symptoms of sprue was demonstrated.