Determination of 58Co-vitamin B12 absorption in pernicious anemia by use of whole-body counting: Reproducibility and control of gut transit time.

In 15 patients with pernicious anemia, the fractional retention of 58Co-cyanocobalamin (FRB12) without administration of intrinsic factor (IF) averaged 4.9% (range 0-12.7). With administration of IF, FRB12 averaged 32.7% (range 26.6--42.3) in the patients and 65.6% (range 38.8--84.6) in 16 control subjects. The gut transit time for vitamin B12 was evaluated from the excretion of radiopaque pellets given concomitantly with the 58Co-vitamin B12. The retention of the pellets was positively correlated to that of the non-absorbed 58Co-B12. Control of the gut transit time is recommended at each examination of FRB12 in order to avoid falsely high values due to the retention of non-absorbed 58Co-B12. We found a good reproducibility of FRB12 when determined in fasting subjects, and it is therefore unnecessary to give the patients a B12-free meal prior to the examination. As the FRB12 in all probability is only a little lower than the fractional absorption, the present method is applicalble for the determination of B12 absorption.