MALABSORPTION AND DEFICIENCY OF VITAMIN-B-12 IN HIV-INFECTED PATIENTS WITH CHRONIC DIARRHEA

Deficiency of vitamin B-12 is commonly reported in HIV-infected patients. We measured vitamin B-12 levelsin 36 HIV-infected patients with chronic diarrhea (>3 stools/day for six weeks or more). Eight patients had an identifiable cause of diarrhea. Vitamin B-12 levels were low in 39%. Sixteen of these patients were selected to undergo further testing, eight patients with low levels of vitamin B-12 and eight with normal B-12 levels. These 16 patients had both a stage II Schilling test and measurement of multiple serum D-xylose concentrations performed after both oral and intravenous doses of D-xylose. Integrated areas under the curves (AUC) for D-xylose concentration versus time were calculated for intravenous and dral doses, and D-xylose bioavailability was determined. Stage II Schilling tests were abnormal in 11 patients, (69%). D-Xylose bioavailability correlated closely with vitamin B-12 absorption (r = 0.648, P < 0.01). Comparisons of mean values for CD4 count, serum albumin, Karnovsky score, six-month weight loss, 1-hr serum D-xylose levels and MCV failed to reveal a significant difference between those with and without abnormal serum vitamin B-12 levels. These data indicate that below-normal levels of vitamin B-12 are highly prevalent in HIV-infected patients with chronic diarrhea. Malabsorption of vitamin B-12 occurs in the setting of an enteropathic process effecting both the proximal and distal small bowel. Since no risk factors for vitamin B-12 deficiency could be identified, screening for vitamin B-12 deficiency in HIV-infected patients with chronic diarrhea is strongly recommended.