Abstract
A vitamin B_<12> absorption test by simultaneous administration of human gastric juice (intrinsic factor)-bound ^<57>Co-B_<12> and free ^<58>Co-B_<12> was carried out in 10 control subjects, 5 patients with pernicious anemia, 1 with total gastrectomy and 4 with malabsorption syndrome. The test is equivalent to two Schilling tests with and without added intrinsic factor, but it is done in one test with the use of two isotopes. Radioactivities of two labels were measured in plasma and urine with time, and in 24 hour urine. Maximum radioactivities were found 8〜10 hours after oral administration. The 24 hour urinary excretion in the control was 17.4±7.3% for ^<58>Co-B_<12> and 17.9±6.0% for ^<57>Co-B_<12>, with a^<57>Co/^<58>Co ratio of close to unity. In malabsorption syndome, urinary excretion of both were extremely low but the ratio was almost unity. In pernicious anemia and in subjects with total gastrectomy, urinary excretion of ^<58>Co-B_<12> was 2.1±1.1%, and ^<57>Co/^<58>Co was 6.2±5.1. Thus, this dual isotope method is of diagnostic value similar to Schilling test done on two occasions. However, it was also found that some of the gastric juice bound B_<12> is exchanged in the digestive tract with free B_<12> and, that to minimize such errors, it is recommended that two doses be given with a two hours interval. In patients in whom complete urinary collection is difficult, or the flushing dose is unwanted, measurement of 8 hour plasma radioactivity may serve the same purpose.
