Objective: To examine the frequency of small bowel bacterial overgrowth in elderly subjects.
Design: Prospective observational study.
Setting: Department of Health Care of the Elderly in a university teaching hospital.
Patients: Thirteen elderly control subjects having undergone normal gastroscopy with normal hematology and anthropometry; 39 consecutive referrals of elderly patients with clinical or biochemical evidence of malnutrition.
Main outcome measures: Duodenal bacterial counts and the 14C-glycocholate, hydrogen, and 14C-xylose breath tests.
Results: Five of the 13 control subjects and 21 of 39 patients with malnutrition had high duodenal bacterial counts (greater than 10(5) organisms/mL), whereas only seven patients were judged to have clinically significant bacterial overgrowth. The 14C-xylose breath test showed a high specificity (89%) but a low sensitivity (30%) when compared with the results of duodenal culture. The hydrogen breath tests and the 14C-glycocholate test showed a similar picture of moderately high specificity and low sensitivity (77% and 20%, respectively, for the hydrogen breath test, 76% and 33%, respectively, for the 14C-glycocholate test).
Conclusions: A positive xylose breath test was the best predictor of high duodenal bacterial counts. However, since many elderly subjects have high duodenal bacterial counts, the overdiagnosis of bacterial overgrowth syndrome will result if duodenal culture is relied upon exclusively.