Korean panic disorder severity scale: construct validity by confirmatory factor analysis

The Panic Disorder Severity Scale (PDSS) is a seven-item instrument used to rate the overall severity of panic disorder. This scale has previously evidenced excellent psychometric properties in a sample of patients with panic disorder, with or without agoraphobia. However, despite several factor-analytic PDSS studies, the number of factors has not been entirely consistent. Our objective in this study, then, was to evaluate the fit of two competing models to data collected with a sample of 176 patients with panic disorder. Patients (N = 176) who fulfilled DSM-IV criteria for panic disorder, with or without agoraphobia, underwent structured diagnostic assessments and PDSS interviews. Of the subjects, 102 were men and 74 were women. The mean age of the men was 41.2 (SD = 10.10) and of women, 41.0 (SD = 10.54). A model with two correlated factors was considered to be more appropriate in the description of the data with the following indices: Tucker-Lewis index = 0.94, comparative fit index = 0.96, root-mean-square error of approximation=0.08, and standardized root-mean-square residual = 0.04. These results were then cross-validated with subgroups of patients with panic disorder with agoraphobia (n = 128), without agoraphobia (n = 48), and with panic disorder after phamacotherapy (n = 62). Our results indicated that the correlated two-factor model developed and validated using Western samples could be appropriately generalized to Korean clinical samples. Furthermore, our results support the construct validity of the Korean version of the PDSS.