New Clinical Method for Distinguishing D-IBS from Other Gastrointestinal Conditions Causing Diarrhea: The LA/IBS Diagnostic Strategy

Modern methods of diagnosing diarrhea-predominant irritable bowel syndrome (D-IBS) require a “diagnosis of exclusion” approach. In this study we aim to test the diagnostic ability of using the fluctuation of frequency and consistency of bowel patterns in IBS to discriminate it from other causes of diarrhea. Eligible subjects were asked to complete a questionnaire on the changes in form and frequency of bowel habits by time. The primary endpoint was to evaluate the diagnostic effectiveness of having irregularly irregular bowel function and form as more characteristic of IBS versus non-IBS causes. Patients were prospectively recruited from a tertiary care GI clinic. Subjects had to have diarrhea as their primary complaint. In the case of IBS, D-IBS subjects were recruited. Subjects with celiac disease, Crohn’s and ulcerative colitis were recruited for comparison and were categorically called “non-IBS.” Non-IBS subjects could not have a recent history of blood in stool or a history of bowel surgery, fistulae or narcotic use. Sixty-two IBS and 37 non-IBS subjects were recruited. Among the 62 IBS subjects, 49 (79%) stated that their bowel habits varied in form and frequency on a daily basis compared to 35% in non-IBS subjects (OR = 8.9,CI = 3.5–22.5, P < 0.00001). When subjects were compared by the number of different stool forms they had witnessed in the prior week, IBS subjects noted 3.58 ± 0.19 types and non-IBS reported 2.35 ± 0.16 (P < 0.00001). Using ≥3 stool forms per week as a method of discriminating IBS from non-IBS, 50 out of 62 subjects with IBS (81%) reported this greater number of forms compared to 15 out of 37 (41%) non-IBS subjects (sensitivity = 0.81; specificity = 0.60). The use of this simple tool that identifies an irregularly irregular bowel form and function is successful in separating D-IBS from non-IBS subjects.