What workup should be considered for patients with chronic diarrhea?
Although an algorithm to guide the workup is not offered, the American Gastroenterological Association suggests the following tests for patients with chronic diarrhea (i.e., watery diarrhea for at least four weeks): fecal calprotectin or fecal lactoferrin to screen for inflammatory bowel disease (IBD), and testing for giardiasis, celiac disease, and bile acid diarrhea. They do not recommend screening for ova and parasites unless the patient has come from a high-risk area. They also recommend against using erythrocyte sedimentation rate (ESR) and C-reactive protein to screen for IBD. (Level of Evidence = 5)
This guideline was developed by a team comprising two gastroenterologists, a primary care physician, and a methodologist, but no patient representative. They performed a systematic review and graded the level of evidence using the GRADE (Grading of Recommendations Assessment, Development, and Evaluation) methodology. One team member reported financial relationships with companies that make diagnostic or treatment products for gastrointestinal disorders. In patients with chronic diarrhea, the group suggests screening for IBD using fecal calprotectin or fecal lactoferrin, but not ESR or C-reactive protein (conditional recommendation based on low-quality evidence). They also recommend testing for Giardia (strong recommendation based on high-quality evidence), but recommend against testing for ova or other parasites unless the patient is from or has traveled to a high-risk area (conditional recommendation based on low-quality evidence). They also suggest testing for celiac disease (strong recommendation based on moderate-quality evidence) and testing for bile acid diarrhea by assay or by an empiric trial of a bile acid binder (conditional recommendation based on low-quality evidence). The group does not recommend a specific order of testing.
Study design: Practice guideline
Funding source: Foundation
Setting: Various (guideline)
Reference: Smalley W, Falck-Ytter C, Carrasco-Labra A, et al. AGA clinical practice guidelines on the laboratory evaluation of functional diarrhea and diarrhea-predominant irritable bowel syndrome in adults (IBS-D). Gastroenterology. 2019;157(3):851–854.