[May the Schilling test be already repeated the next day using intrinsic factor?].

The effect of previous administration of a dose of 1000 mu-g vitamin B12 on the Schilling test was examined in 18 patients, repeating the test 24 hrs later. On the first day 57-Co was administered, while on the second day 58-Co labeled vitamin B12 was given. The counting error was less than 2.0% at the 95% confidence level. A decrease in urinary excretion of vitamin B12 of 28.7 plus or minus 22.2% (x plus or minus SD) was found. The mean difference between the two subsequent Schilling test series was statistically significant (p less than 0.05). The excretion data of the first and the second test correlate well (r = 0.86; p less than 0.01; y = 0.66 x + 1.09). Thus the repeated Schilling test with intrinsic factor must not be performed the next day.