The American Gastroenterological Association (AGA) has published updated practice guidelines on laboratory evaluation of patients with functional diarrhea and diarrhea-predominant irritable bowel syndrome (IBS-D).

These guidelines are applicable for the evaluation of the immunocompetent patient with “watery” diarrhea of at least 4 weeks duration. They exclude patients with bloody diarrhea; diarrhea with signs of fat malabsorption; presentations with alarm features (weight loss, anemia, and hypoalbuminemia); 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.

In patients presenting with chronic diarrhea, the AGA:

• Suggests the use of either fecal calprotectin (threshold value of 50 mg/g) or fecal lactoferrin (threshold value of 4.0–7.25 mg/g) to screen for IBD.        
• Suggests against the use of erythrocyte sedimentation rate (ESR) or C-reactive protein (CRP) to screen for IBD. CRP may be an option where testing for fecal lactoferrin or calprotectin are either not available or not covered by insurance.         
• Recommends testing for Giardia using a Giardia antigen test or polymerase chain reaction.
• Suggests against testing stools for ova and parasites (other than Giardia) in patients presenting with chronic diarrhea with no travel history to or recent immigration from high-risk areas. 
• Recommends testing for celiac disease with IgA- tissue transglutaminase (tTG) and a second test to detect celiac disease in the setting of IgA deficiency       
• Suggests testing for bile acid diarrhea.

The AGA makes no recommendation for the use of currently available serologic tests for diagnosis of IBS in patients with chronic diarrhea.

(Source: Gastroenterology. 2019;157(3):851-4)

Dr KK Aggarwal

Padma Shri Awardee

President Confederation of Medical Associations in Asia and Oceania (CMAAO)

Group Editor-in-Chief IJCP Publications

President Heart Care Foundation of India

Past National President IMA