Reliability and validity of the Korean version of the Impact of Event Scale-Revised.

Objectives: The aim of this study was to explore the reliability and validity of the Impact of Event Scale-Revised Korean version (IES-R-K), a self-report scale for assessment of posttraumatic stress disorder (PTSD).

Methods: The original Impact of Event Scale-Revised was translated into Korean, and the comparability of content was verified through back-translation procedures. This multicenter study included 93 patients with PTSD, 73 nonpsychotic psychiatric patients, and 88 healthy controls drawn from 18 hospitals across the country. The subjects were assessed using IES-R-K, Clinician-Administered PTSD Scale (CAPS), Beck Depression Inventory, and State Trait Anxiety Inventory (STAI; state anxiety subscale [STAI-S], trait anxiety subscale [STAI-T]) scales.

Results: In the reliability test, Cronbach alpha coefficient and test-retest reliability were .93 and 0.91, respectively, indicating that the IES-R-K has good internal consistency. One-way analysis of variance revealed significant differences in IES-R-K scores among the patients with PTSD, nonpsychotic psychiatric patients, and healthy controls (F = 139.1, P < .001). Duncan post hoc test showed the significant differences among the 3 groups. To assess the validity of the IES-R-K, correlation coefficient between the IES-R-K and CAPS, STAI-S, and STAI-T was calculated. We found that there was a relatively high degree of correlation between the IES-R-K and CAPS (r = 0.92, P < .001). However, there was a relatively less degree of correlation between STAI-S and STAI-T and IES-R-K (r = 0.30, P < .001). Taken these together, IES-R-K showed good discriminant validity.

Conclusion: The IES-R-K showed good reliability and validity for the assessment of PTSD symptom severity. The IES-R-K is a useful instrument for assessing PTSD symptoms in Korea.