Millions of people suffer from the effects of irritable bowel syndrome (IBS) — chronic bloating, abdominal pain, gas, diarrhea or constipation — although the malady itself, let alone the cause, has been notoriously difficult to diagnose. Now, however, a physician at Cedars-Sinai Medical Center in Los Angeles has developed two blood tests that can accurately detect the problem and have the results back to the patient’s doctor within 24 hours. The new tests, called IBSchek, will also detect whether a person developed IBS symptoms from a foodborne pathogen.