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Item Response Theory Analysis of the Posttraumatic Stress Disorder Symptoms Assessed by Posttraumatic Stress Disorder Checklist for DSM-5 (PCL-5)

Recent changes in the DSM-5 diagnostic criteria for Posttraumatic Stress Disorder (PTSD) symptoms has led to a substantial amount of empirical research supporting alternative models encompassing an increasing number of symptomatic clusters (from 1 to 7; Rasmussen, Verkuilen, Jayawickreme, Wu, & McCluskey, 2019). Simultaneously, studies analyzing whether the DSM-5 PTSD symptoms converge to a single latent structured in order to make a global PTSD diagnosis are still scare. Thus, this study intended to analyze the unidimensionality of DSM-5 PTSD symptoms through Item Response Theory. METHOD Participants and procedures: a convenience sample of 446 firefighters (currently active professional and volunteers), between18 and 62 years old (M = 35.53; SD = 10.12) and 4 to 22 years of education (M = 11.02; SD = 3.03), was recruited at fire departments across the Portuguese mainland and island territories. Participation was voluntary and compliant with research ethical standards. Measure: PTSD Checklist for the DSM-5 (PCL-5; Weathers et al., 2013; Carvalho, da Motta, & Pinto-Gouveia, 2019). The PCL-5 is a 20-item self-report measure that assesses the severity PTSD symptoms in the last month on a 5-point scale. The Portuguese version is internally consistent (α =.94). Data analysis: Rasch Model (RM) was used to assess the measure of PTSD symptoms. Goodness of model fit for items and persons were evaluated according to the following criteria: Infit and Outfit > 2.0 degrade the measurement; 1.5 2.0 unproductive for measurement; 0.5 1.5 productive for measurement; < 0.5 are less productive for measurement, but not degrading. Differential item functioning (DIF) analysis was carried out between participants who scored above and below 33 points (current suggested cutoff point for provisional PTSD diagnosis, according to the original authors). Item Response Theory Analysis of the Posttraumatic Stress Disorder Symptoms assessed by Posttraumatic Stress Disorder Checklist for DSM-5 (PCL-5)