Diagnostic Testing in Irritable Bowel Syndrome: Theory vs. Reality

By: Brennan M.R. Spiegel, M.D., VA Greater Los Angeles Healthcare System; David Geffen School of Medicine at UCLA; UCLA/VA Center for Outcomes Research and Education (CORE), Los Angeles, CA

Dr. Spiegel is the recipient of the 2007 IFFGD Research Award for Junior Investigator – Clinical Science. His current research is looking at ways to improve the quality and cost-effectiveness of care for patients with IBS and other functional GI disorders.

Summary

Although irritable bowel syndrome (IBS) is extremely prevalent, affecting up to 15% of the general population, diagnosing IBS is not always straightforward. Properly diagnosing IBS can be challenging and uncertain for several reasons.

Despite the tendency to order diagnostic tests in the face of IBS symptoms, the diagnostic criteria for IBS, such as those supported by the Rome Committee, encourage clinicians to make a positive diagnosis on the basis of validated symptom criteria, and emphasize that IBS is not a diagnosis of exclusion despite the extensive list of other conditions that masquerade as IBS.

The current Rome guidelines for IBS state that IBS can be diagnosed in the absence of 'alarm features,' and is 'often properly diagnosed without testing.' When alarm features are present, the diagnosis of IBS should not be made. However, the part about diagnosing IBS 'without testing' can be murky ground for clinicians. This uncertainty leads to rampant diagnostic testing in IBS.

Why do providers continue to order tests in IBS, despite data that these tests are generally low yield? That is, why is there mismatch between academic theory and clinical reality? Assuming there are no alarming signs or symptoms, clinicians should focus less on diagnostic testing and focus more on education and treatment.

Ultimately, patients and their doctors should use their judgment, and must reserve the right to investigate further if the IBS doesn’t 'follow the script,' so to speak, either because of a poor response to therapy, worsening of symptoms over time despite treatment, or development of new alarming features. Like most things in medicine, diagnostic testing in IBS remains a balance of art and science.