Use of the lactose-[13C]ureide breath test for diagnosis of small bowel bacterial overgrowth: comparison to the glucose hydrogen breath test

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-[C-13]ureide breath test (LUBT) to diagnose SBBO and to compare it with the GHBT, using cultures of intestinal aspirates as a gold standard. 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-[C-13]ureide, end-expiratory breath samples were obtained up to 120 min. The C-13/C-12 ratio in breath CO2 was determined by isotope ratio-mass spectrometry and hydrogen concentration in breath was analyzed electrochemically. 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 a parts per thousand yen12 ppm from baseline was considered positive. The sensitivity and specificity of the test were 41.7 and 44.4%, respectively. 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.