Diagnosis of Microscopic Colitis in Patients With Irritable Bowel Syndrome Subtype Diarrhea: A Case Control Propensity Matched Study

Introduction: Prior studies have suggested significant symptom overlap between IBS-D and MC. We aimed to determine the odds of MC in a subset of patients with a diagnosis of IBS-D using the updated Rome IV Criteria compared to controls (patients with diarrhea not meeting diagnostic criteria for IBS-D) Methods: We conducted a propensity matched case-control study. Cases were IBS-D patients diagnosed by Rome IV criteria. Controls were patients with diarrhea that did not fulfill the Rome IV diagnostic criteria for IBS-D. We recorded information on patients’ socio-demographic, risk factors for MC and comorbidities for cases and controls. Only patients who had a colonoscopy were included in the analysis. Controls were matched with cases by age and sex using a Greedy 2:1 matching algorithm. An exact conditional logistic regression model was used to compare MC between the 2 cohorts. Results: A pre-match total of 432 patients (cases n= 374, controls n =58) met inclusion criteria. Before matching (Table 1), patients in the control cohort were older than patients in the case cohort (P < .001), and there were more male patients in the control cohort (n = 155/374 or 41.4%) than case cohort (n = 15/58 or 25.9%; P = .02). Despite higher occurrence of MC noted in pre-matched controls (5.1%) compared to cases (1.7%), there was no significant difference in the rate of MC between the 2 cohorts (P = .50). Following the matching algorithm (Table 1), the cases and controls were well balanced on age and sex (all standardized difference scores < 0.25) and there remained no difference in the rate of MC between the 2 cohorts (1.7 vs 1.7 %, P = .99) Conclusion: Prior studies using the Rome III criteria, showed no difference in occurrence of MC in IBS-D patients compared to age and sex matched controls. Although the Rome IV criteria was developed to address the shortcomings of Rome III, our study did not show a significant difference in the occurrence of MC in IBS-D cases compared to age and sex matched controls. Our results do not support the use of routine colonoscopy to evaluate for MC in IBS-D patients due to uncertain benefits and low prevalence of MC in IBS-D. However, in highly selected patients, colonoscopy should still be considered to rule out MC as a potential etiology for symptoms. Future research should focus on identifying less invasive, cost effective, and more precise biological or non-biological markers to diagnose MC in patients with IBS-D. Table 1. - Pre and Post-Match Summary Statistics Pre-match Summary Statistics Control (n = 374) Case (n = 58) p StandardizedDifference Age 52.7 (15.0) 40.7 (13.5) < .001 0.84 Sex .02 0.33 Female 219 (58.6%) 43 (74.1%) Male 155 (41.4%) 15 (25.9%) Microscopic Colitis .50 0.19 No 355 (94.9%) 57 (98.3%) Yes 19 (5.1%) 1 (1.7%) Post-match Summary Statistics Control (n = 116) Case (n = 58) p StandardizedDifference Age 40.9 (13.1) 40.7 (13.5) 0.01 Sex 0.00 Female 86 (74.1%) 43 (74.1%) Male 30 (25.9%) 15 (25.86) Microscopic Colitis .99 0.00 No 114 (98.3%) 57 (98.3%) Yes 2 (1.7%) 1 (1.7%)