The blood test for Diarrhea-predominant IBS detects antibodies of two toxins that are released by food poisoning bacteria. These toxins induce diarrhea.

In a trial involving 2,700 patients with IBS, inflammatory bowel disease (IBD), or celiac disease as well as healthy controls, the test, showed positive predictive values "north of 98%" for IBS said Mark Pimentel, MD, of Cedars-Sinai Medical Center in Los Angeles.
Pimentel explained that the test detects antibodies to cytolethal distending toxin B (CdtB) and vinculin, which are released by bacteria that cause food poisoning. Many earlier studies have shown that food borne bacterial infections can lead to IBS by triggering an autoimmune reaction, he said.
Patients often undergo a long diagnostic odyssey to establish a diagnosis as the symptoms of IBS are non-specific and are also seen in IBD and celiac disease. Instead of endoscopies, the blood test would quickly rule out IBD and benefit patients by reducing the cost, inconvenience, and discomfort associated with colonoscopies.
Source-Medindia