2.2.1. Impact of Event Scale—Revised, IES-R

The IES-R was developed by Horowitz et al. [7] and revised by Weiss et al. [8] into a 22-item self-report scale including 8 items for intrusion, 8 items for avoidance, and 6 items for hyperarousal, each being rated on a 5-point (0–4) scale. Sometimes, however, the items have been classified differently depending on the exploratory or confirmatory factor analysis carried out by various studies [6,9,14,16]. Higher scores are interpreted as having more severe post-traumatic stress.

Eun et al. [6] and Lim et al. [9] had translated the IES-R into Korean, and Park et al. [18] revised the adapted scales based on consultations with psychiatric specialists to improve the content validity and face validity of the tools. This study applied the tool developed by Park et al. [18] to nurses who performed COVID-19-related tasks and conducted confirmatory factor analysis referring to the results of Weiss et al. [8], Eun et al. [6], and Lim et al. [9], as well as additional exploratory factor analysis. This study used 18 points as the cutoff score for partial PTSD, which Eun et al. [6] had reported.