D-xylose malabsorption: characteristic finding in patients with the AIDS wasting syndrome and chronic diarrhea

The AIDS wasting syndrome (AWS) is characterized by > 10% loss of baseline body weight during 6 months and may occur in patients with or without associated chronic diarrhea. To determine whether the presence of small-intestinal malabsorption is associated with the development of AWS in human immunodeficiency virus (HIV)-infected patients with chronic diarrhea, we retrospectively reviewed the results of D-xylose testing performed in the clinical evaluation of 21 consecutive HIV-infected patients with chronic diarrhea. A thorough search for small-intestinal pathogens was performed including upper endoscopy, duodenal biopsy, and aspirate for culture and ova and parasite examination. These studies were negative in all patients except two who were excluded from the study. In the 19 patients with no identifiable pathogens, the 1-h serum D-xylose concentration was significantly lower in patients with AWS than in those without, 8.3 +/- 0.8 versus 23.7 +/- 3.4 mg/dl, respectively, p < 0.001. Urine D-xylose excretion during 5 h was also significantly lower in the group with AWS, although creatinine clearance was similar in the two groups. Patients with AWS were more often refractory to standard antidiarrheal therapy with loperamide or diphenoxylate and carried a poor prognosis (90% mortality at 1 year versus 22% mortality in the group without AWS). These data indicate that small intestinal malabsorption is a major component in the severe wasting seen in some HIV-infected patients with chronic diarrhea. Patients with markedly abnormal D-xylose tests may require more potent antidiarrheal therapy and are expected to have a high mortality as a possible consequence of intestinal dysfunction.