Laboratory evaluation of functional diarrhea and diarrhea with IBS in adults: AGA Guidelines

American Gastroenterological Association has released its guidelines on Laboratory evaluation of functional diarrhea and diarrhea with IBS in adults.This document presents the official recommendations of the American Gastroenterological Association (AGA) on the Laboratory Evaluation of Functional Diarrhea and Diarrhea-Predominant Irritable Bowel Syndrome (IBS-D) in Adults. The guideline was developed by the AGA’s Clinical Practice Guideline Committee and approved by the American Gastroenterological Association Governing Board. These Guidelines should expire in 5 years.

The focus of this guideline is to aid clinicians in choosing appropriate laboratory tests to exclude other diagnoses in the setting of suspected functional diarrhea or IBS-D. These guidelines apply to the evaluation of the immunocompetent patient with “watery” diarrhea of at least 4 weeks duration. This would exclude those patients with bloody diarrhea; diarrhea with signs of fat malabsorption; presentations with alarm features, such as weight loss, anemia, and hypoalbuminemia; those patients with a family history of inflammatory bowel disease (IBD), colon cancer, or celiac disease; and those with a travel history to regions with recognized specific diarrhea-related pathogens.

Current evidence supports the use of fecal calprotectin or fecal lactoferrin and stool testing for Giardia in patients presenting with chronic diarrhea. The panel suggests against the use of blood tests ESR or CRP to screen for IBD. Our evidence profiles also strongly recommend testing for celiac disease with IgA-tTG and a second test to detect celiac disease in the setting of IgA deficiency. In addition, testing for bile acid diarrhea is suggested. The AGA makes no recommendation for the use of currently available serologic tests for the diagnosis of IBS and should be the focus of future research. A clinical decision support tool is included to guide the evaluation of patients with chronic watery diarrhea (>4 weeks).

1. In patients presenting with chronic diarrhea, the American Gastroenterological Association suggests the use of either fecal calprotectin or fecal lactoferrin to screen for IBD.

2. In patients presenting with chronic diarrhea, the American Gastroenterological Association suggests against the use of erythrocyte sedimentation rate or C-reactive protein to screen for IBD.

3. In patients presenting with chronic diarrhea, the American Gastroenterological Association recommends testing for Giardia. Strong recommendation: high-quality evidence.