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

Deficiency of vitamin B-12 is commonly reported in HIV-infected patien ts. We measured vitamin B-12 levelsin 36 HIV-infected patients with ch ronic diarrhea (>3 stools/day for six weeks or more). Eight patients h ad an identifiable cause of diarrhea. Vitamin B-12 levels were low in 39%. Sixteen of these patients were selected to undergo further testin g, eight patients with low levels of vitamin B-12 and eight with norma l B-12 levels. These 16 patients had both a stage II Schilling test an d measurement of multiple serum D-xylose concentrations performed afte r both oral and intravenous doses of D-xylose. Integrated areas under the curves (AUC) for D-xylose concentration versus time were calculate d for intravenous and dral doses, and D-xylose bioavailability was det ermined. Stage II Schilling tests were abnormal in 11 patients, (69%). D-Xylose bioavailability correlated closely with vitamin B-12 absorpt ion (r = 0.648, P < 0.01). Comparisons of mean values for CD4 count, s erum albumin, Karnovsky score, six-month weight loss, 1-hr serum D-xyl ose levels and MCV failed to reveal a significant difference between t hose with and without abnormal serum vitamin B-12 levels. These data i ndicate that below-normal levels of vitamin B-12 are highly prevalent in HIV-infected patients with chronic diarrhea. Malabsorption of vitam in B-12 occurs in the setting of an enteropathic process effecting bot h the proximal and distal small bowel. Since no risk factors for vitam in B-12 deficiency could be identified, screening for vitamin B-12 def iciency in HIV-infected patients with chronic diarrhea is strongly rec ommended.