New blood test can quickly diagnose irritable bowel syndrome

itable bowel syndrome, the most common gastroenterological disorder in the US, can now be diagnosed with just two simple blood tests, enabling early diagnosis for millions of people affected by the disorder.

Symptoms of IBS include abdominal pain and unpredictable bouts of diarrhea and constipation.

Until now, irritable bowel syndrome (IBS) has only been diagnosed after a long and drawn out process of ruling out other conditions, often involving invasive procedures such as colonoscopies and sigmoidoscopies.

Researchers at Cedars-Sinai in Los Angeles, CA, created the tests. They explain that as there have been no definitive tests for IBS, patients have frequently had to go from doctor to doctor, repeating tests before they have been able to get a diagnosis they are confident with.

Having an early diagnosis means patients can avoid years of invasive tests and visits to specialists that often leave them with more questions than answers. With these new blood tests, many patients will now be able to proceed right to therapy for their condition.

Around 10% of the global population is estimated to have IBS, with around 10-15% of the US population affected. The condition is characterized by a variety of symptoms that includes abdominal pain, bloating and bouts of diarrhea and constipation that can cause stress and fatigue.

Imagine a patient who wakes up in the morning and doesn't know when they're going to have a bowel movement, if it's going to be diarrhea or constipation. Are they going to be at a restaurant with friends? Are they going to be in a meeting? I mean, it's very traumatic because it's unpredictable in terms of the function.

The tests, developed by the researchers  over the course of 8 years, identify when IBS has developed by recognizing the presence of specific antibodies - anti-Cdtb and anti-vinculin - that react to toxins associated with food poisoning. These toxins, produced by bacteria such as salmonella, damage nerves that are vital to healthy gut functioning.

Tests detect biomarkers with greater than 90% accuracy

To validate the accuracy of the blood tests, the researchers analyzed nearly 3,000 people aged 18-65, comparing participants with IBS with people with inflammatory bowel disease, celiac disease or no gastrointestinal disease at all.

The researchers found that the blood tests identified anti-Cdtb and anti-vinculin antibodies successfully with greater than 90% accuracy. These antibodies were elevated in participants with IBS compared with participants that did not have IBS.

As a result, the researchers state that these biomarkers may be especially helpful in distinguishing IBS from inflammatory bowel disease in the workup of chronic diarrhea.

The authors acknowledge that the new tests are limited by a lower specificity for identifying IBS compared with celiac disease, though they suggest this problem is easily solved by testing for celiac disease antibodies alongside the IBS tests.

The study is published in PLOS ONE, and the researchers presented the findings at Digestive Disease Week 2015 in Washington, DC.

For the 40 million Americans who have irritable bowel syndrome, they now have a test that says 'You have IBS, it's real, it's an organic disease, it's not a psychological disorder,' and they can go straight to therapy, or at least get an answer.

References:

1.  Development and validation of a biomarker for diarrhea-predominant irritable bowel syndrome in human subjects, Mark Pimentel, et al., PLOS ONE, doi: 10.1371/journal.pone.0126438, published online 13 May 2015.
2.  Cedars-Sinai news release, accessed 20 May 2015.
3.  Additional source: Mayo Clinic, Irritable bowel syndrome - tests and diagnosis, accessed 20 May 2015.