Mechanisms of vitamin B12 deficiency in elderly inpatients.

A protein-bound Schilling test incorporating chick serum was used to study 16 elderly vitamin B12-deficient inpatients. Thirteen of these also underwent standard Schilling tests. They were compared with an age-matched control group of non-deficient inpatients. The lower limit of normal for assimilation of protein-bound vitamin B12 was 0.7%. Fourteen out of 16 deficient patients assimilated protein-bound vitamin B12 subnormally. Twelve of these were fully Schilling tested. Five assimilated free B12 normally, and five responded to intrinsic factor. One patient did not respond to intrinsic factor and had jejunal diverticulosis and one could not be categorized. One of two patients with normal assimilation had a borderline vitamin B12 intake. No subjects had neurological sequelae and only three were anaemic. In this population, B12 deficiency is usually asymptomatic but nearly always results from impaired assimilation possibly justifying replacement therapy. Schilling testing only affects treatment if there is other evidence of small-bowel dysfunction.