A Breakthrough in IBS Etiology … and the Test That Resulted

For a problem as common as irritable bowel syndrome (IBS)—it affects as many as 1 in 5 people—you would think there would be more diagnostic tools available to detect its presence. However, IBS has historically been a diagnosis of exclusion, because its symptoms, including bloating, gassiness, and intermittent stomach pain, can have other causes, such as celiac disease. This makes a differential diagnosis for IBS particularly difficult, and possibly lengthy and expensive. Patients who seek medical attention for IBS frequently undergo years of invasive and exploratory tests such as body imaging or endoscopy to rule out organic causes.

This may be changing for the better, however. Several years ago, researchers observed a connection between IBS and infection: 40% of patients who were diagnosed with IBS-D (diarrhea-predominant IBS) had had a previous bout of acute gastroenteritis or food poisoning.1 This led to a better understanding of the pathogenesis of at least some types of IBS:

  • Gastroenteritis-related bacteria produce the neurotoxin CdtB (cytolethal distending toxin B).
  • The immune system produces antibodies that attack CdtB.
  • These antibodies cross-react with vinculin, a protein lining the intestinal tract.
  • The lining is degraded, leading to small intestinal bacterial overgrowth (SIBO).
  • SIBO manifests as bloating and abdominal pain, the first symptoms of IBS.

This breakthrough led to the validation of two serum biomarkers, anti-CdtB and anti-vinculin, which are now detectable through the IBSDetex™ test from Quest Diagnostics. IBSDetex measures anti-CdtB and anti-vinculin to confirm post-infectious IBS-D or IBS-M (mixed IBS, or IBS with diarrhea and constipation) as a source of patient symptoms. This means you now have an additional tool for an IBS diagnostic workup that:

  • Can help differentiate IBS from celiac disease
  • May be especially helpful in distinguishing IBS-D from inflammatory bowel disease in the workup of chronic diarrhea
  • May point to effective treatment, as these patients may be treatable with antibiotics

IBSDetex is noninvasive and results are available in as little as 72 hours from receipt of the specimen. As a reminder, although IBS is common, people at greater risk include those under 45, female (IBS is twice as common in women as in men), and with a family history of IBS.

Last, remember that many patients with IBS go undiagnosed. They are unlikely to bring up IBS-like symptoms with you because they attribute their symptoms to diet, stress, or anxiety. Particularly for patients where a family history of IBS is noted, IBS may be a topic worth bringing up—especially now that there is an inclusionary tool to confirm a diagnosis.

Interested? Learn more about IBSDetex, including how to interpret results.


1. Pimentel M, Morales W, Rezaie A, et al. Development and validation of a biomarker for diarrhea-predominant irritable bowel syndrome in human subjects. PLoS ONE. 2015;10:e0126438..