MDCalc

Laboratory Evaluation of Functional Diarrhea and Diarrhea-Predominant Irritable Bowel Syndrome in Adults (IBS-D)

Based on guidelines from the American Gastroenterological Association. Use to evaluate an immunocompetent patient with complaints of "watery" diarrhea of at least 4 weeks duration.

Diagnosis

Testing
Strong recommendation
Moderate quality evidence
In patients presenting with chronic diarrhea, the AGA recommends testing for celiac disease with IgA-tTG and a second test to detect celiac disease in the setting of IgA deficiency.
Clinical Comment: Testing options for IgA-deficient subjects include IgG tissue transglutaminase and IgG or IgA deaminated gliadin peptides.
Strong recommendation
High quality evidence
In patients presenting with chronic diarrhea, the AGA recommends testing for Giardia.
Clinical Comment: Use of a Giardia antigen test or polymerase chain reaction for Giardia test is recommended.
Conditional recommendation
Low quality evidence
In patients presenting with chronic diarrhea with no travel history to or recent immigration from high-risk areas, the AGA suggests against testing stools for ova and parasites (other than Giardia).
Conditional recommendation
Low quality evidence
In patients presenting with chronic diarrhea, the AGA suggests testing for bile acid diarrhea.
Clinical Comment: In settings with limited availability of commercial assays, an empiric trial of a bile acid binder could be considered.
No recommendation
Evidence gap
In patients presenting with chronic diarrhea, the AGA makes no recommendation for the use of currently available serologic tests for diagnosis of IBS.
Conditional recommendation
Low quality evidence
In patients presenting with chronic diarrhea, the AGA suggests the use of either fecal calprotectin or fecal lactoferrin to screen for IBD.
Clinical Comment: A threshold value of 50 μg/g for fecal calprotectin is recommended to optimize sensitivity for IBD. Threshold values in the range of 4.0–7.25 μg/g for fecal lactoferrin are recommended to optimize sensitivity.
Conditional recommendation
Low quality evidence
In patients presenting with chronic diarrhea, the AGA suggests against the use of erythrocyte sedimentation rate (ESR) or serum C-reactive protein (CRP) to screen for IBD.
Literature
Original/Primary Reference
Research PaperSmalley W, Falck-Ytter C, Carrasco-Labra A, Wani S, Lytvyn L, Falck-Ytter Y. 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.