Ability of lactulose breath test results to accurately identify colorectal polyps through the measurement of small intestine bacterial overgrowth

Abstract

Background: While colorectal polyps are not cancerous, some types of polyps, known as adenomas, can develop into colorectal cancer over time. Polyps can often be found and removed by colonoscopy; however, this is an invasive and expensive test. Thus, there is a need for new methods of screening patients at high risk of developing polyps.

Aim: To identify a potential association between colorectal polyps and small intestine bacteria overgrowth (SIBO) or other relevant factors in a patient cohort with lactulose breath test (LBT) results.

Methods: A total of 382 patients who had received an LBT were classified into polyp and non-polyp groups that were confirmed by colonoscopy and pathology. SIBO was diagnosed by measuring LBT-derived hydrogen (H) and methane (M) levels according to 2017 North American Consensus recommendations. Logistic regression was used to assess the ability of LBT to predict colorectal polyps. Intestinal barrier function damage (IBFD) was determined by blood assays.

Results: H and M levels revealed that the prevalence of SIBO was significantly higher in the polyp group than in the non-polyp group (41% vs 23%, P < 0.01; 71% vs 59%, P < 0.05, respectively). Within 90 min of lactulose ingestion, the peak H values in the adenomatous and inflammatory/hyperplastic polyp patients were significantly higher than those in the non-polyp group (P < 0.01, and P = 0.03, respectively). In 227 patients with SIBO defined by combining H and M values, the rate of IBFD determined by blood lipopolysaccharide levels was significantly higher among patients with polyps than those without (15% vs 5%, P < 0.05). In regression analysis with age and gender adjustment, colorectal polyps were most accurately predicted with models using M peak values or combined H and M values limited by North American Consensus recommendations for SIBO. These models had a sensitivity of ≥ 0.67, a specificity of ≥ 0.64, and an accuracy of ≥ 0.66.

Conclusion: The current study made key associations among colorectal polyps, SIBO, and IBFD and demonstrated that LBT has moderate potential as an alternative noninvasive screening tool for colorectal polyps.

Keywords: Colorectal polyp; Intestinal barrier function; Lactulose breath test; Retrospective study; Small intestine bacteria overgrowth.

Figure 1

Rate of intestinal barrier function damage in 227 small intestine bacteria overgrowth patients. ^aThe rate of intestinal barrier function damage (IBFD) by 3 blood assays altogether was marginally higher in polyp group than that in non-polyp group, but no significance, P = 0.13. ^bIt was significantly different between polyp group and non-polyp group when IBFD defined by lipopolysaccharide alone, P < 0.05. SIBO: Small intestine bacteria overgrowth; DAO: Diamine oxidase; LPS: Lipopolysaccharide.

Figure 2

The receiver operation characteristic curves for age and gender adjusted performance of prediction models. A-G: Each model is for a subset of patient population defined by the cutoffs and the size of the subpopulation showing at the top of each box.