Key Points From the AGA Guideline for Laboratory Evaluation of Functional and IBS-D in Adults

Vanessa M. Shami, MD, FASGE reviewing Smalley W, et al. Gastroenterology 2019 July 11.

Chronic diarrhea of functional etiology is a commonly encountered outpatient GI diagnosis. Unfortunately, the optimal laboratory evaluation of chronic diarrhea is not standardized. In the present article, the American Gastroenterological Association (AGA) provides recommendations for assessment of suspected functional diarrhea or diarrhea-predominant IBS (IBS-D). These recommendations apply to patients with watery diarrhea of at least 4 weeks duration and exclude those with alarm features, such as bleeding, steatorrhea, weight loss, anemia, or hypoalbuminemia. Further excluded are patients with a family history of colon cancer, celiac disease, or recent travel to regions with endemic enteric pathogens.

Takeaways/recommendations:

  • Consider ordering fecal calprotectin or fecal lactoferrin to screen for IBD. The recommendation is conditional, and the evidence is low quality.
  • Routinely ordering an erythrocyte sedimentation rate or C-reactive protein is not recommended to screen for IBD. The recommendation is conditional, and the evidence is low quality.
  • Testing for Giardia using either the Giardia antigen test or polymerase chain reaction is recommended. The recommendation is strong, and the evidence is high quality. 
  • Routine testing for ova and parasites (other than Giardia) is not recommended in patients with no history of travel to high-risk areas. The recommendation is conditional, and the evidence is low quality. 
  • Testing for celiac disease with tissue transglutaminase IgA and total serum IgA is recommended. The recommendation is strong, and the evidence is moderate quality.   
  • Consider testing for bile acid diarrhea. This may entail an empiric trial of bile acid binders, especially when specific laboratory testing is not available. The recommendation is conditional, and the evidence is low quality. 
  • Routine testing with serologic tests for a diagnosis of postinfectious IBS-D is not recommended. There is insufficient evidence for a recommendation.

Comment:

These important guidelines give us much-needed assistance on the diagnostic laboratory approach to patients suspected of having IBS-D.

Note to readers:
At the time we reviewed this paper, its publisher noted that it was not in final form and that subsequent changes might be made.

Vanessa M. Shami, MD, FASGE
Bio and Disclosures

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Citation(s):
Smalley W, Falck-Ytter C, Carrasco-Labra A, Wani S, Lytvyn L, Falck-Ytter Y. AGA guideline on the laboratory evaluation of functional diarrhea and diarrhea-predominant irritable bowel syndrome in adults (IBS-D). Gastroenterology 2019 July 11. (Epub ahead of print) (https://doi.org/10.1053/j.gastro.2019.07.004)