Content Validity and Psychometric Evaluation of the Crohn's Symptom Severity (CSS) Questionnaire in Patients with Moderately to Severely Active Crohn's Disease.

Introduction: Individuals living with Crohn's disease (CD) experience burdensome symptoms. As such, it is important to measure CD symptom severity in clinical research. The goal of this study was to evaluate the content validity, psychometric performance, and score interpretability of a new patient-reported instrument, the Crohn's Symptom Severity (CSS) questionnaire, among adolescents and adults with moderately to severely active CD.

Methods: Cognitive debriefing interviews (N = 30; n = 20 adults, n = 10 adolescents) were conducted to evaluate the content validity of the CSS. Additionally, the CSS scores were evaluated for reliability and validity using data from a phase 3 randomized clinical trial of risankizumab (NCT03105128; N = 850). Meaningful within-patient change (MWPC) thresholds were estimated using anchor-based methods.

Results: All interview participants (n = 30/30, 100.00%) reported the CSS was easy to complete and most participants (n = 28/29, 96.55%) reported that the CSS was relevant to their experience of CD. Among the clinical trial subjects (N = 850) the following was found for the CSS: mostly acceptable item-total correlations (0.26-0.79); weak to moderate inter-item correlations (r = 0.07-0.57), good internal consistency (Cronbach's α = 0.76-0.87); intraclass correlation coefficients ranged from 0.48 to 0.70, not consistently exceeding the acceptable range for test-retest reliability (0.70); acceptable convergent validity and known-groups results; and demonstrated sensitivity to change. Analyses supported an MWPC estimate of 6-11 points.

Conclusions: This study supports use of the CSS for measuring CD symptoms and sleep impact among adolescents and adults aged 16 and older with moderately to severely active CD in clinical research.

Trial registration: NCT03105128 (registration date 4 April 2017).