Abstract
BACKGROUND: The aims of this study were to conduct a cross-cultural validation of the Panic Disorder Severity Scale - Self-Report (PDSS-SR) and to examine psychometric properties of the French-Canadian version. METHODS: A sample of 256 adults were included in the validation study based on data from the baseline interview of a clinical trial on transdiagnostic cognitive-behavioral therapy for mixed anxiety disorders. Participants completed the Anxiety and Related Disorders Interview Schedule (ADIS-5), and self-report instruments including the PDSS-SR, Beck Anxiety Inventory (BAI), Mobility Inventory for Agoraphobia (MIA), Sheehan Disability Scale (SDS), Patient Health Questionnaire (PHQ-9), Social Phobia Inventory (SPIN), Insomnia Severity Index (ISI) and Penn State Worry Questionnaire (PSWQ). The cross-cultural adaptation in French of the PDSS-SR included a rigorous back-translation process, with an expert committee review. Sensitivity to change was also examined with a subgroup of patients (n = 72) enrolled in the trial. RESULTS: The French version of the PDSS-SR demonstrated good psychometric properties. The exploratory factor analysis supported a one factor structure with an eigenvalue > 1 that explained 64.9% of the total variability. The confirmatory factor analysis (CFA) corroborated a one-factor model with a good model fit. Internal consistency analysis showed a .91 Cronbach's alpha. The convergent validity was adequate with the ADIS-5 clinical severity ratings for panic disorder (r = .56) and agoraphobia (r = .39), as well as for self-report instruments [BAI (r = .63), MIA (accompanied: r = .50; alone: r = .47) and SDS (r = .37)]. With respect to discriminant validity, lower correlations were found with the SPIN (r = .17), PSWQ (r = .11), ISI (r = .19) and PHQ-9 (r = .28). The optimal threshold for probable diagnosis was 9 for the PDSS-SR and 4 for the very brief 2-item version. The French version showed good sensitivity to change. CONCLUSIONS: The French version of the PDSS-SR has psychometric properties consistent with the original version and constitutes a valid brief scale to assess the severity of panic disorder and change in severity over time, both in research and clinical practice.