Reduced Accuracy of ¹⁴C-D-Xylose Breath Test for Detecting Bacterial Overgrowth in Gastrointestinal Motility Disorders

Abstract

The accuracy of the ¹⁴C-D-xylose breath test in the diagnosis of small-bowel bacterial overgrowth was prospectively evaluated in 10 patients with motility disorders: 6 myopathic, 3 neuropathic, and 1 mechanical obstruction. Six of the 10 patients had small-bowel bacterial overgrowth (≥10⁵ colony-forming units/ml) on culture of small-bowel aspirate. Increased breath ¹⁴CO₂ levels were documented in three of six patients with positive cultures and in two of four with negative cultures. Two patients with positive results by both methods and one of two patients with positive breath ^l4CO₂ but negative cultures had previously undergone gastric surgery. Three patients with myopathic dysmotility had positive cultures but negative breath tests. Cultures of duodenal aspirates and the D-xylose test had sensitivities of 80% and 40%, respectively, for the finding of hypoalbuminemia. Compared with cultures, the sensitivity and specificity of the breath test were 60% and 40%, respectively. Impaired delivery of ^l4C-D-xylose for bacterial metabolism may result from postprandial antral hypomotility (n = 4) or low-amplitude (n = 6) small-bowel motility, contributing to the false-negative breath tests. Thus, culture is the optimal method to detect small-bowel bacterial overgrowth in patients with motility disorders.

Key Words:

• Bacterial overgrowth
• motility disorders