Blood Tests for Diagnosing IBS

person getting blood drawn
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Recent headlines have been announcing that there is now a blood test for IBS, a disorder that has traditionally been diagnosed based on symptoms and the absence of other digestive diseases. Before you go running off to have your blood drawn, let's take a look at what the buzz is all about.

The Tests

Dr. Mark Pimentel and his team of researchers have come up with a way to test blood samples of patients who are experiencing symptoms of chronic diarrhea for the presence of certain biomarkers as a way to diagnose IBS.

The tests are only able to make such a diagnosis in patients whose symptoms developed after a case of acute gastroenteritis, such as food poisoning, a condition known as post-infectious IBS. However, the tests do seem to provide the advantage of helping to quickly and accurately differentiate between a diagnosis of IBS and one of inflammatory bowel disease (IBD) for such individuals.

The Science Behind the Tests

The tests were based on emerging research that after an intestinal infection there are changes in the makeup of gut bacteria, which for some people results in the development of diarrhea-predominant IBS (IBS-D). The researchers posit that the bacteria that was behind the original illness produce toxins which then cause damage to the nerves within the intestines and thus contribute to ongoing symptoms. In response to these toxins, our bodies produce antibodies. These new blood tests were designed to measure the presence and amount of two such antibodies: anti-CdtB and anti-vinculin.

The Research

As of now, the validity of these blood tests seem to be based on one study conducted by Dr. Pimentel and his team. The study design involved comparing blood samples from 2375 individuals who were diagnosed with IBS-D, with 142 of those with IBD, 121 people with celiac disease, and 43 individuals with no diagnosed digestive disorder.

The results indicated that the presence of both anti-CdtB and anti-vinculin antibodies was significantly higher in the blood of those who had IBS-D as compared to the other three groups. Based on these results, the researchers conclude that these tests are a valid way to diagnose IBS-D. Interestingly, the tests seemed to be a little better at differentiating between IBS-D and IBD then they were for differentiating between IBS-D and celiac disease. (This is not a big problem as there is another blood biomarker for a celiac diagnosis.)

However, the study also indicates that some cases of IBS-D would not be identified, while a small number of individuals would receive a false positive result. It is also important to keep in mind that this is just one study, with small numbers of participants in each study group.

The Bottom Line

It is great that this research seems to provide some definitive evidence that IBS is an organic disease, not just something in a person's head! The potential ability to get a quick and accurate diagnosis will bring about great relief for people who find themselves with ongoing digestive problems after a bad stomach but. And the possibility that there may be an option to quickly and relatively painlessly differentiate between cases of IBS and IBD will allow people to have quicker access to appropriate treatment.

However, at this point, these tests represent an imperfect, early test of a particular, small group of IBS patients - those whose symptoms can be traced to an acute gastrointestinal infection. 

Hopefully, more clinical trials will be conducted to provide further evidence of the validity of these blood tests, in general, and with a variety of study populations. And it is unfortunate that the test is only of use for cases of post-infectious IBS. Hopefully, further research will identify other biomarkers so as to provide a quicker and easier diagnosis process for those with other types of IBS.


Pimentel, M., "Development and Validation of a Biomarker for Diarrhea-Predominant Irritable Bowel Syndrome in Human Subjects" PLOS One 10:e0126438.

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