Irritable bowel syndrome (IBS) is the most common chronic gastrointestinal disorder. Reported prevalence of IBS is approximately 15% of the population and annual incidence rate of 200 per 100,000 people.1 IBS accounts for 10% to 15% of primary care visits and 25% to 50% of gastroenterology referral visits.2  In general, IBS is considered a “functional condition” in the absence of a known cause or “organic” biomarker.  Based on the bowel habits similar distribution is found among, constipation predominant IBS (IBS-C), diarrhea predominant IBS (IBS-D), and IBS mixed between diarrhea and constipation (IBS-M). Role of acute gastroenteritis and alterations in the intestinal microbiota is recently linked with the pathogenesis of IBS-D. 

Antibody to cytotoxic distending toxin B (CdtB) and to vinculin are the first and serological tests for IBS-D and IBS-M.3  Not only is this testing useful in affirmatively diagnosing IBS in the setting of unexplained diarrhea, it is also possible to now to diagnose IBS coexisting with other conditions characterized by diarrhea, e.g. IBD and celiac disease.3  Having an affirmative test for IBS is critical to establish a diagnosis of coexisting IBS especially when other causes of diarrhea such as inflammatory bowel disease (IBD) or celiac disease co-exist.3  

Most (76.6%) irritable bowel syndrome sufferers in the US are undiagnosed.  Irritable bowel syndrome has a substantial impact on sufferers' well-being and health.  This testing will now enable doctors to identify patients with IBS-D and IBS-M and treat accordingly. 

Learning Objectives

  • Physicians will learn about the new blood test from Quest Diagnostics to diagnose IBS-diarrhea and mixed predominant.
  • They will also learn how this test can be integrated into a work up of the patients who present with chronic gastrointestinal including IBD and celiac disease. 
  • Additionally obtain more information about ordering IBSDetex. 
  • To understand the pathogenesis of IBS, role of this novel blood test in diagnosis of post infectious IBS, mechanization of the test and how to order it.


  1. Choung RS, G. and Locke RG. Epidemiology of IBS. Gastroenterol Clin N Am 40 (2011) 1–10. . 
  2. Talley NJ, Zinsmeister AR, Van Dyke C, et al. Epidemiology of colonic symptoms and the irritable bowel syndrome. Gastroenterology 1991;101(4):927–34.
  3. Pimentel M, Morales W, Rezaie A, Marsh E, Lembo A, Mirocha J, etal. Development and validation of a biomarker for diarrhea-predominant irritable bowel syndrome in human subjects. PLoS One. 2015;10:e0126438.