Applications of the Schilling test and saturation analysis techniques to the investigation of absorption and transport of vitamin B-12 in Ugandans. Part of a coordinated programme on in vitro assay techniques

The absorption of Vitamin B12 in 21 subjects was investigated, using the Schilling test. One microgramme of radioactive Vitamin B12 followed by a flushing dose of 1000 mcg after 2 hours resulted in very low urinary excrection rates. Different flushing doses were administered to 11 asymptomatic volunteers at different times after the active dose. Adequate excretion was obtained when a flushing dose of 5000 mcg of B12 was given five hours after the active dose. In 23 other subjects this combination was found to give excretion rates comparable to those found in other populations where the usual procedure had been used. Plasma and urine patterns of radioactivity showed that, when the standard method was used, there was no failure of vitamin absorption but flushing from the plasma was poor. Flushing was more effective with the modified procedure. An additional binder in the plasma of Ugandans is likely; its effect may have combined with the previously demonstrated slow rate of absorption of vitamin to make the modified method effective and the standard one ineffective. A new procedure for the Schilling test is therefore proposed for this population since the standard method would be unsuitable