title: Predicting a Response to Antibiotics in Patients with the Irritable Bowel Syndrome.
abstract: BACKGROUND
  Antibiotics for presumed small intestinal bacterial overgrowth have been shown to improve irritable bowel syndrome symptoms in at least 40% of subjects. A lactulose breath test for small intestinal bacterial overgrowth has been used to select patients who will respond. However, its predictive value, using the classic definition of a positive lactulose breath test, has been disappointing.
  
  
  OBJECTIVE
  We conducted a retrospective evaluation to study characteristics of the lactulose breath test that may be predictive of a response to antibiotics in patients with the irritable bowel syndrome.
  
  
  METHODS
  A clinical practice database was interrogated for consecutive patients who had a lactulose breath test for irritable bowel syndrome symptoms and a subsequent antibiotic course. Hydrogen + methane levels with carbon dioxide correction were plotted against time. Various profiles of the breath test curves were catalogued and compared with respect to their predictive value for symptom response to antibiotics.
  
  
  RESULTS
  Lactulose breath test graphs of 561 patients of all irritable bowel syndrome subtypes were grouped into categories based on their hydrogen + methane levels with respect to time. Of subjects whose hydrogen + methane rise was <20 ppm throughout the test (group 1; N = 95), 94.7% improved after antibiotics (95% CI 90.1-99.3). Of those with a rise <20 ppm within the first 90 min but a rise >50 ppm thereafter (group 3; N = 53), 47.2% improved (95% CI 33.7-60.6). The difference between groups 1 and 3 was statistically significant P < 0.001.
  
  
  CONCLUSIONS
  A lactulose breath test appears to be useful in predicting response to antibiotics in patients with the irritable bowel syndrome. A hydrogen + methane rise <20 ppm throughout the duration of the test is most predictive. This observation contradicts the classic definition of a positive lactulose breath test.
authors.affiliation: Connecticut Gastroenterology Institute, 39 Brewster Road, Bristol, CT, 06010, USA. rkasir@uchc.edu.
authors.forename: Rafid
authors.initials: R
authors.lastname: Kasir
authors.affiliation: Connecticut Gastroenterology Institute, 39 Brewster Road, Bristol, CT, 06010, USA. szakko@bristolhospital.org.
authors.forename: Salam
authors.initials: S
authors.lastname: Zakko
authors.affiliation: Connecticut Gastroenterology Institute, 39 Brewster Road, Bristol, CT, 06010, USA.
authors.forename: Philip
authors.initials: P
authors.lastname: Zakko
authors.affiliation: Connecticut Gastroenterology Institute, 39 Brewster Road, Bristol, CT, 06010, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Adler
authors.affiliation: Connecticut Gastroenterology Institute, 39 Brewster Road, Bristol, CT, 06010, USA.
authors.forename: Aaron
authors.initials: A
authors.lastname: Lee
authors.affiliation: Connecticut Gastroenterology Institute, 39 Brewster Road, Bristol, CT, 06010, USA.
authors.forename: Sachin
authors.initials: S
authors.lastname: Dhingra
authors.affiliation: Connecticut Gastroenterology Institute, 39 Brewster Road, Bristol, CT, 06010, USA.
authors.forename: Cecile
authors.initials: C
authors.lastname: Guttermuth
mesh_terms: D000328:Adult; D000368:Aged; D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D001424:Bacterial Infections / Q000150:complications / Q000188:drug therapy*; D001944:Breath Tests; D003248:Constipation / Q000188:drug therapy* / Q000209:etiology / Q000382:microbiology; D003967:Diarrhea / Q000188:drug therapy* / Q000209:etiology / Q000382:microbiology; D005260:Female; D000069196:Gastrointestinal Microbiome; D006801:Humans; D006859:Hydrogen / Q000032:analysis; D043183:Irritable Bowel Syndrome / Q000150:complications / Q000188:drug therapy* / Q000382:microbiology; D007792:Lactulose; D008297:Male; D008697:Methane / Q000032:analysis; D008875:Middle Aged; D012189:Retrospective Studies; D016896:Treatment Outcome
chemical_list: D000900:Anti-Bacterial Agents; D007792:Lactulose; D006859:Hydrogen; D008697:Methane
keywords: Antibiotics; Flat line; IBS; Irritable bowel syndrome; Lactulose breath test; SIBO; Small intestinal bacterial overgrowth