Since 1952, Co60 cyanocobalamin (vitamin B12) has been used to confirm the diagnosis of pernicious anemia. Its main advantage is that it is an effective diagnostic agent whether or not cyanocobalamin or liver extract has been taken as a form of treatment. It is in this particular group of patients who have been given treatment and in whom the ordinary diagnostic laboratory tests have been obscured by the effects of the therapy that this test is particularly useful.
Four methods for measuring the absorption of orally administered radioactive cyanocobalamin are currently used. After the oral administration of Co60 cyanocobalamin, measurement of radioactivity in the stool,1 hepatic uptake of Co60 cyanocobalamin,2,3 and recovery of the radioactive cyanocobalamin in the urine4 have all been used. Recently Co56 cyanocobalamin has been measured in the plasma after oral administration.5 Schilling's method of measuring Co60 cyanocobalamin in a 24-hour urine sample has been widely adopted