ABSTRACT
PURPOSE: Symptom heterogeneity in interstitial cystitis/bladder pain syndrome and chronic prostatitis/chronic pelvic pain syndrome, collectively termed urological chronic pelvic pain syndrome, has resulted in difficulty in defining appropriate clinical trial endpoints. We determine clinically important differences for 2 primary symptom measures, pelvic pain severity and urinary symptom severity, and evaluate subgroup differences. MATERIALS AND METHODS: The Multidisciplinary Approach to the Study of Chronic Pelvic Pain Symptom Patterns Study enrolled individuals with urological chronic pelvic pain syndrome. We defined clinically important differences by associating changes in pelvic pain severity and urinary symptom severity over 3 to 6 months with marked improvement on a global response assessment using regression and receiver operating characteristic curves. We evaluated clinically important differences for absolute and percent change and examined differences in clinically important differences by sex-diagnosis, presence of Hunner lesions, pain type, pain widespreadness, and baseline symptom severity. RESULTS: An absolute change of -4 was clinically important in pelvic pain severity among all patients, but clinically important difference estimates differed by pain type, presence of Hunner lesions, and baseline severity. Pelvic pain severity clinically important difference estimates for percent change were more consistent across subgroups and ranged from 30% to 57%. The absolute change urinary symptom severity clinically important difference was -3 for female participants and -2 for male participants with chronic prostatitis/chronic pelvic pain syndrome only. Patients with greater baseline severity required larger decreases in symptoms to feel improved. Estimated clinically important differences had lower accuracy among participants with low baseline symptoms. CONCLUSIONS: A reduction of 30%-50% in pelvic pain severity is a clinically meaningful endpoint for future therapeutic trials in urological chronic pelvic pain syndrome. Urinary symptom severity clinically important differences are more appropriately defined separately for male and female participants.