Measurement nonequivalence of the Clinician-Administered PTSD Scale by race/ethnicity

Abstract

Research studies suggest racial/ethnic differences in posttraumatic stress disorder (PTSD) diagnosis and symptom severity. Few studies to date, however, have examined the extent to which these findings are due to differences in measurement properties of existing PTSD scales. This study examined measurement equivalence across race/ethnicity in the Clinician-Administered PTSD Scale (CAPS) by testing for differential item functioning (DIF) in the item response theory (IRT) framework. Participants were 506 trauma-exposed women (M = 39.41 years, SD = 8.94) who participated in the National Drug Abuse Treatment Clinical Trials Network Women and Trauma Study. PTSD severity score estimates were improved upon as part of IRT estimation incorporating symptom "weights" (i.e., factor loadings) and group-specific DIF. Six symptoms from the CAPS showed DIF, with the majority of differences in measurement driven by White/African American and White/Latina differences, particularly for (a) avoidance of thoughts and (b) a sense of foreshortened future. Despite both racial/ethnic minority groups being slightly (not significantly) more likely to receive a PTSD diagnosis, African Americans (p = .014; Cohen's d = -.22) and Latinas (p = .001; d = -.73) had significantly lower PTSD severity scores than Whites as estimated under IRT with group-specific DIF. Examination of PTSD severity scores based on symptom counts revealed these differences were either dampened (White/Latina difference d = -.39) or entirely negated (White/African American difference d = -.08). The findings suggest the importance of considering differences in symptom relevance across race/ethnicity and their impact on capturing symptom severity parallel to diagnostic criteria. Implications for clinical practice are discussed.Public Significance Statement The current study examined measurement equivalence across race/ethnicity in the Clinician-Administered PTSD Scale by testing for differential item functioning in the item response theory framework. The findings suggest that considering differences in posttraumatic stress disorder (PTSD) symptom relevance across race/ethnicity is critical for increasing accuracy in diagnostic criteria and estimation of PTSD severity.