Use of the Lactose-[13C]ureide Breath Test for Diagnosis of Small Bowel Bacterial Overgrowth: Comparison to the Glucose Hydrogen Breath Test

Purpose: The glucose hydrogen breath test (GHBT) is commonly used as a noninvasive test to diagnose small bowel bacterial overgrowth (SBBO) but its validity has been questioned. Our aim was to evaluate the lactose-[(13)C]ureide breath test (LUBT) to diagnose SBBO and to compare it with the GHBT, using cultures of intestinal aspirates as a gold standard.

Methods: In 22 patients with suspected SBBO (14 male, age range 18-73 years) aspirates were taken from the region of the ligament of Treitz under sterile conditions and cultured for bacterial growth. More than 10(6) colony-forming units/mL fluid or the presence of colonic flora was defined as culture positive (c+). After oral intake of 50 g glucose and 2 g of lactose-[(13)C]ureide, end-expiratory breath samples were obtained up to 120 min. The (13)C/(12)C ratio in breath CO(2) was determined by isotope ratio-mass spectrometry and hydrogen concentration in breath was analyzed electrochemically.

Results: After analyzing receiver operating characteristic curves of the LUBT results, total label recovery of >0.88% at 120 min was considered positive. The test had a sensitivity of 66.7% and a specificity of 100% to predict c+. In the GHBT, an increase of the signal of > or =12 ppm from baseline was considered positive. The sensitivity and specificity of the test were 41.7 and 44.4%, respectively.

Conclusions: The new stable isotope-labeled LUBT has excellent specificity but suboptimal sensitivity. In contrast, the standard GHBT lacks both high sensitivity and specificity. The LUBT is superior to the GHBT for detecting SBBO.