What is the role of lab tests in the workup of irritable bowel syndrome (IBS)?

Updated: Dec 30, 2019
  • Author: Mohammad F El-Baba, MD; Chief Editor: Carmen Cuffari, MD  more...
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No specific laboratory markers are noted for irritable bowel syndrome (IBS). [1] Patients who have characteristic symptoms and meet the Rome criteria for irritable bowel syndrome (see History) do not require a thorough diagnostic evaluation. A more aggressive approach is recommended for individuals with atypical symptoms, those with a rapidly progressive course, or when the index of suspicion for an organic disease is high.

In classic cases, a limited screen for organic disease is reassuring and should consist of the following:

  • Complete blood cell (CBC) count

  • Erythrocyte sedimentation rate

  • Stool studies for ova and parasites

  • Stool cultures and stool Clostridium difficile toxin assay, if clinically indicated

  • A breath hydrogen test or a trial of dietary lactose restriction to exclude lactose intolerance

The following laboratory tests are indicated in special instances:

  • Lead level assessment

  • Celiac serologic tests

  • Serum immune markers for inflammatory bowel disease

  • Thyroid function tests

  • Tests for Helicobacter pylori (ie, serum antibody titers, urea breath test)

Studies have suggested that determining the level of fecal calprotectin in stool may help distinguish irritable bowel syndrome from inflammatory bowel disease. A negative calprotectin result favors a functional disorder rather than an inflammatory process, thereby sparing many patients from having extensive work-up and invasive investigations, such as colonoscopy. [24]

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