Spotlight on irritable bowel syndrome

Irritable bowel syndrome (IBS) was the focus of two recent studies, which analyzed patients with symptoms of diarrhea-predominant IBS (IBS-D) and IBS after infectious enteritis.

In the IBS-D study, researchers compared the clinical characteristics of patients diagnosed with IBS-D according to Rome III criteria and undiagnosed patients with comparable symptoms. In September 2014, 1,924 U.S. participants (1,094 diagnosed and 830 undiagnosed) completed the online survey, which assessed symptoms, health care utilization, health-related quality of life, treatments, and perceived explanations for GI symptoms. Results of the industry-funded study were published online on Jan. 17 by the American Journal of Gastroenterology.

Compared to undiagnosed patients, those who received a diagnosis were more likely to have severe GI symptoms (16% vs. 8%, P<0.05) and report experiencing GI symptoms for 10 or more years (55% vs. 18%, P<0.05). Among participants who were undiagnosed, 53% reported that they had never spoken with a physician about their GI symptoms, whereas diagnosed patients reported consulting a greater number of physicians and gastroenterologists (P<0.05 for all comparisons).

The study authors noted that a formal IBS-D diagnosis seems to be important, highlighting their findings that diagnosed patients were offered more treatments and seemed to have greater access to evidence-based therapies. They added that diagnosed patients seemed to be better informed about their condition, reporting more scientifically derived explanations for their symptoms (e.g., diet, genetics, and intestinal microbiota) than undiagnosed individuals. Limitations of the study include its survey-based design, cross-sectional nature, and lack of access to patient medical records (i.e., diagnoses were not confirmed).

The other study, a systematic review and meta-analysis published online on Jan. 6 by Gastroenterology, examined the prevalence, risk factors, and outcomes of IBS after foodborne illness and other forms of infectious enteritis. Researchers identified 45 studies of 21,421 individuals with infectious enteritis who were followed for three months to 10 years for the development of IBS.

The overall pooled prevalence of postinfectious IBS was 11.5% (95% CI, 8.2% to 15.8%). Compared to individuals without infectious enteritis, the overall risk of IBS was 4.2-fold higher in patients who had infectious enteritis in the past 12 months (95% CI, 3.1 to 5.7) and 2.3-fold higher in those affected more than 12 months ago (95% CI, 1.8 to 3.0). Overall, the rates of IBS were highest after protozoal/parasitic infectious enteritis (about 40%), followed by bacterial and then viral infectious enteritis. Given a conservative estimate of 15% of the U.S. population being exposed to infectious enteritis annually, approximately 1.6% or 5.1 million people would develop new-onset IBS each year based on this study's findings, the study authors wrote.

The authors noted that clinicians should consider postinfectious IBS when caring for patients with chronic GI symptoms after an episode of infectious enteritis, especially in those at high risk: women, patients with prevalent anxiety and depression at the time of infection, those with clinically severe infectious enteritis, and those treated with antibiotics. Limitations of the analysis include its cross-sectional nature, high heterogeneity among studies, and adjustment for different confounding variables across studies.