It is common for patients with Small Intestinal Bacterial Overgrowth (SIBO) to have symptomatologies that overlap with Irritable Bowel Syndrome (IBS). SIBO is defined as the presence in the small intestine of excessive gut bacteria that originates from the colon. Similar to IBS there is currently no definite test for the diagnosis of SIBO. The jejunal aspirate and bacterial culture test as well as the breath test after administration of fermentable substrate are both problematic and suffer from many false positives and some false negative results. Therefore, there is a need for a blood test for the determination of IBS/SIBO.