Diagnostic Value of Radioactive Vitamin B12

Summary The intestinal absorption of orally administered radioactive vitamin B12 has been studied by a modified urinary excretion test. Subjects were given a standard oral dose of 0.6 microgramme of 60Co vitamin B12. The mean 48‐hour urinary radioactivity in 22 control individuals was 23.9% of the oral dose. In five patients with megaloblastic anæmia due to folic acid deficiency, a similar mean excretion of 22 4% was found. In 15 patients with pernicious anæmia in relapse, impaired absorption of radioactive vitamin B12 was demonstrated. The mean urinary radioactivity was 2.4%. This was increased to 19.6% when the oral dose was given with an intrinsic factor preparation. Twenty‐five patients on maintenance therapy because of a previous diagnosis of pernicious anæmia were studied. The diagnosis was disproved in to patients, who were shown to be able to absorb orally administered radioactive vitamin B12 normally.