The Canadian Association of Gastroenterology (CAG) recently co-published a clinical practice guideline for the management of bile acid diarrhea (BAD) in Clinical Gastroenterology and Hepatology and the Journal of the Canadian Association of Gastroenterology.
Given a minimal evidence base, 16 out of the 17 guideline recommendations are conditional, according to lead author, of Royal Alexandra Hospital, Edmonton, Alta., and colleagues. Considering the shortage of high-quality evidence, the panel called for more randomized clinical trials to address current knowledge gaps.
“BAD is an understudied, often underappreciated condition, and questions remain regarding its diagnosis and treatment,” the panelists wrote in. “There have been guidelines on the management of chronic diarrhea from the American Gastroenterological Association, and the British Society of Gastroenterology, but diagnosis and management of BAD was not assessed extensively in these publications. The British Society of Gastroenterology updated guidelines on the investigation of chronic diarrhea in adults, published after the consensus meeting, addressed some issues related to BAD.”
For the current guideline, using available evidence and clinical experience, expert panelists from Canada, the United States, and the United Kingdom aimed to “provide a reasonable and practical approach to care for specialists.” The guideline was further reviewed by the CAG Practice Affairs and Clinical Affairs Committees and the CAG Board of Directors.
The guideline first puts BAD in clinical context, noting a chronic diarrhea prevalence rate of approximately 5%. According to the guideline, approximately 1 out of 4 of these patients with chronic diarrhea may have BAD and prevalence of BAD is likely higher among those with other conditions, such as terminal ileal disease.
While BAD may be relatively common, it isn’t necessarily easy to diagnose, the panelists noted.
“The diagnosis of BAD continues to be a challenge, although this may be improved in the future with the general availability of screening serologic tests and other diagnostic tests,” the panelists wrote. “Although a treatment trial with bile acid sequestrants therapy (BAST) often is used, this approach has not been studied adequately, and likely is imprecise, and may lead to both undertreatment and overtreatment.”
Instead, the panelists recommended testing for BAD with 75-selenium homocholic acid taurine (SeHCAT) or 7-alpha-hydroxy-4-cholesten-3-one.
After addressing treatable causes of BAD, the guideline recommends initial therapy with cholestyramine or, if this is poorly tolerated, switching to BAST. However, the panelists advised against BAST for patients with resection or ileal Crohn’s disease, for whom other antidiarrheal agents are more suitable. When appropriate, BAST should be given at the lowest effective dose, with periodic trials of on-demand, intermittent administration, the panelists recommended. When BAST is ineffective, the guideline recommends that clinicians review concurrent medications as a possible cause of BAD or reinvestigate.
Concluding the guideline, the panelists emphasized the need for more high-quality research.
“The group recognized that specific, high-certainty evidence was lacking in many areas and recommended further studies that would improve the data available in future methodologic evaluations,” the panelists wrote.
While improving diagnostic accuracy of BAD should be a major goal of such research, progress is currently limited by an integral shortcoming of diagnostic test accuracy (DTA) studies, the panelists wrote.
“The main challenge in conducting DTA studies for BAD is the lack of a widely accepted or universally agreed-upon reference standard because the condition is defined and classified based on pathophysiologic mechanisms and its response to treatment (BAST),” the panelists wrote. “In addition, the index tests (SeHCAT, C4, FGF19, fecal bile acid assay) provide a continuous measure of metabolic function. Hence, DTA studies are not the most appropriate study design.”
“Therefore, one of the research priorities in BAD is for the scientific and clinical communities to agree on a reference standard that best represents BAD (e.g., response to BAST), with full understanding that the reference standard is and likely will be imperfect.”
The guideline was funded by unrestricted grants from Pendopharm and GE Healthcare Canada. The panelists disclosed relationships with AstraZeneca, AbbVie, Merck, Pfizer, and others.
Review the AGA clinical practice guideline on the laboratory evaluation of functional diarrhea and diarrhea-predominan irritable bowel syndrome in adults at https:/www.gastrojournal.org/article/S0016-5085(19)41083-4/fulltext.
SOURCE: Sadowski DC et al. Clin Gastroenterol Hepatol. 2019 Sep 14.