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
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.
Clinical Comment: Testing options for IgA-deficient subjects include IgG tissue transglutaminase and IgG or IgA deaminated gliadin peptides.
Strong recommendation
Moderate 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.
Clinical Comment: Use of a Giardia antigen test or polymerase chain reaction for Giardia test is recommended.
Strong recommendation
High 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.
Clinical Comment: In settings with limited availability of commercial assays, an empiric trial of a bile acid binder could be considered.
Conditional recommendation
Low quality evidence
In patients presenting with chronic diarrhea, the AGA makes no recommendation for the use of currently available serologic tests for diagnosis of IBS.
No recommendation
Evidence gap
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.
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.
Conditional recommendation
Low quality evidence
What do the icons mean?
How strong is the AGA's recommendation?
Strong recommendation
Most individuals in this situation would want the recommended course of action, and only a small proportion would not.Conditional recommendation
The majority of individuals in this situation would want the suggested course of action, but many would not.No recommendation
The confidence in the effect estimate is so low that any effect estimate is speculative at this time.High quality evidence
We are very confident that the true effect lies close to that of the estimate of the effect.Moderate quality evidence
We are moderately confident in the effect estimate. The true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different.Low quality evidence
Our confidence in the effect estimate is limited. The true effect may be substantially different from the estimate of the effect.Evidence gap
Available evidence is insufficient to determine true effect.Literature
