Scintigraphy Demonstrates High Rate of False-positive Results From Glucose Breath Tests for Small Bowel Bacterial Overgrowth

Abstract

Background & aims: Breath tests for hydrogen and/or methane are used to detect small bowel bacterial overgrowth (SBBO), but false-positive results can arise from clinical conditions that accelerate small bowel transit and deliver unabsorbed glucose to the colon. We investigated the prevalence of false-positive results from glucose breath tests by also evaluating patients with scintigraphy.

Methods: In a retrospective study, we reviewed data from glucose breath tests performed with concurrent scintigraphy on 139 patients with suspected SBBO at the Medical College of Wisconsin from January 2003 through July 2013. Results from breath tests were considered abnormal (positive) if there was an increasing curve of hydrogen or methane by >15 parts per million above baseline within 90 minutes. Scintigraphy was used to determine whether this increase occurred before or after the glucose bolus arrived at the cecum. Data from a subset of 45 patients with prior upper gastrointestinal surgery were analyzed separately.

Results: Forty-six of the patients (33%) had abnormal results from breath tests. On the basis of scintigraphy findings, 22 of these patients (48%) had false-positive results, which were caused by colon fermentation of unabsorbed glucose. Colon fermentation caused false-positive results in 65% of patients who had undergone upper gastrointestinal surgery and 13% of patients without prior surgery. Patients with false-positive results caused by colonic fermentation had shorter mean oro-cecal transit times (18 minutes) compared with patients with positive breath-test results because of SBBO (79 minutes) or negative results (86 minutes).

Conclusions: Almost half of positive results from glucose breath tests are false because of colonic fermentation. All patients with abnormal results from breath tests should be considered for confirmatory repeat breath testing with concurrent scintigraphy to distinguish SBBO from colonic fermentation. Most patients who have undergone upper gastrointestinal surgery have abnormal results from breath tests and should be assessed by using concurrent scintigraphy with the initial breath test.

Keywords: Accuracy; Analysis; Diagnosis; Diagnostic; Lactulose.