Jim Kling

October 24, 2013

SAN DIEGO — A blood test for antibodies that target the vinculin protein could be used to determine if a condition is related to irritable bowel syndrome (IBS), researchers report. If confirmed, it would be the first serum-based diagnostic test for IBS.

"IBS has suffered from a diagnosis-of-exclusion approach, and has limited clinical criteria," said Mark Pimentel, MD, from the Cedars-Sinai Medical Center in Los Angeles.

That limitation prompted Dr. Pimentel and his team to search for alternative diagnostics. He presented the research here at the American College of Gastroenterology 2013 Annual Scientific Meeting.

Accumulated evidence has indicated that many cases of IBS begin after a bout of acute gastroenteritis. Human and animal studies have suggested that acute gastroenteritis can lead to small intestinal bacterial overgrowth, through neuropathic events. Cytolethal distending toxin B produced by gastroenteritis-causing bacteria plays a role in this process.

Dr. Pimentel's team concluded that antibodies that target cytolethal distending toxin B cross-react to vinculin, which is a cell migration and adherence protein found predominantly on nerves and epithelium. They surmised that this could lead to the nerve damage that underlies IBS.

The researchers conducted a multicenter study to test whether antivinculin antibodies could be used as a biomarker for IBS.

The study cohort involved 165 patients with IBS diagnosed using the Rome criteria, 30 patients with inflammatory bowel disease, and 26 control subjects.

 
IBS has suffered from a diagnosis-of-exclusion approach, and has limited clinical criteria.
 

People with concomitant gastrointestinal disease, adhesions, unstable thyroid disease, diabetes, or HIV were excluded from the study, as were people who had undergone previous gastrointestinal surgery.

When serum from the study subjects underwent enzyme-linked immunosorbent assay (ELISA) testing, the optical density of antivinculin antibodies was found to be significantly greater in patients with IBS than in those with inflammatory bowel disease or healthy subjects.

For patients with IBS, levels of antivinculin antibodies were higher in those with a history of acute gastroenteritis than in those without such a history (< .05).

"From some aspects of our data, we could almost certainly diagnose irritable bowel syndrome," Dr. Pimentel told reporters attending a news conference.

His team is currently conducting research to see if the test can predict bacterial overgrowth in IBS patients, and therefore which patients will respond well to antibiotic therapy.

Not everyone was as enthusiastic about the findings, though.

"The data are very preliminary. When you do case–controlled studies, they always overestimate the accuracy of the test because it's easy. It's easy for us as physicians, so it's easy for the test," said meeting attendee Paul Moayyedi, MD, from McMaster University in Hamilton, Ontario, Canada.

"It's harder when you've got this general population with all sorts of diseases and other things going on to really determine who has IBS." The data don't show that yet, he told Medscape Medical News.

The sensitivity and specificity values were too low to make it a great test, said Dr. Moayyedi. "But I don't want to throw too much cold water on it."

Although we should not be testing patients with it, "this is a start," he noted. The test will get better as epitopes are developed and antibodies are refined or added, he explained.

Dr. Pimentel and Dr. Moayyedi have disclosed no relevant financial relationships.

American College of Gastroenterology (ACG) 2013 Annual Scientific Meeting and Postgraduate Course: Abstract 8. Presented October 14, 2013.

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