The Detection of Intestinal Absorption of Co^57 Tagged Vitamin B_12 by Serum Counting

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Abstract
A modified test for gastrointestinal absorption of vitamin B12 was studied. Eight to 10 hours after oral administration of 0.5 [mu]g of cyanocobalamin tagged with 0.5 [mu][image] of Co57, a serum sample is counted in a well-type scintillation counter. The test may be done concurrently with or without Schilling urinary excretion test. Thirteen patients with Addisionian pernicious anemia had less than 8 cpm/4 ml of serum 8 to 12 hours after the oral radio-cobalamin and 1 had 12 cpm/4 ml. Forty-four patients with normal vitamin B12 absorption had 15 or more cpm/4 ml and usually more than 20. Renal disease did not lead to false results in the serum. Patients with non-Addisionian malabsorption of vitamin B12 had low serum counts but there was no increase in counts when the test was repeated with intrinsic factor as there was in true pernicious anemia. The counts in the serum 8 to 12 hours after an oral dose of Co57 B12 permits as ready a differentiation between normal and reduced absorption of vitamin B12 as does the standard urine excretion test. The serum test avoids errors due to renal disease and inadequate urine collection. It also permits the measurement of B12 absorption without the administration of a large parenteral flushing dose of vitamin B12.