Utility of hydrogen breath tests in diagnosis of small intestinal bacterial overgrowth in malabsorption syndrome and its relationship with oro-cecal transit time.

BACKGROUND Small intestinal bacterial overgrowth (SIBO), which may result from intestinal stasis, is common in malabsorption syndrome (MAS). Quantitative culture of upper gut aspirate is used as a gold standard for the diagnosis of SIBO. Studies on diagnosis of SIBO using non-invasive hydrogen breath tests are contradictory. METHODS 83 patients (age 35 [14-70] y; 50 men) with MAS due to various causes were investigated for SIBO using quantitative culture of upper gut aspirate obtained using a special endoscopic catheter and glucose and lactulose hydrogen breath tests (GHBT, LHBT). Sustained elevation in breath hydrogen of 12 ppm above basal and two separate peaks (one due to SIBO and the other from colon) were diagnostic of SIBO in GHBT and LHBT, respectively. Oro-cecal transit time (OCTT) was estimated using LHBT in 71 patients. RESULTS Thirty two of 81 (39.5%) patients with MAS had SIBO on culture (>or= 10(5) CFU/mL). Using aspirate culture as the gold standard, sensitivity, specificity, positive and negative predictive values and diagnostic accuracy of GHBT to diagnose SIBO were 44%, 80%, 62%, 67% and 65%, respectively; the corresponding values for LHBT were 31%, 86%, 62%, 54% and 55%, respectively. OCTT in patients with SIBO diagnosed on GHBT and/or aspirate culture (n=58) was longer than in those without (170 [60-250] vs. 120 [50-290] min, p=0.02); of others, 7 were hydrogen non-producers and in 6 OCTT could not be assessed due to sustained early peak because of SIBO. CONCLUSIONS GHBT and LHBT are highly specific but insensitive for diagnosis of SIBO in MAS; OCTT is longer in patients with MAS and SIBO than in those without.