Psychometric properties of the Mississippi Scale for Combat-Related Posttraumatic Stress Disorder based on veterans’ period of service.

Abstract

The Mississippi Scale for Combat-Related Posttraumatic Stress Disorder (M-PTSD) is a 35-item screening instrument for combat-related PTSD (Keane, Caddell, & Taylor, 1988) that has been normed largely on veterans from the Vietnam era. Research on its psychometric properties with veterans across different periods of service (POS) remains limited; however, this is an important research endeavor because of the uniqueness in experiences across eras which may influence PTSD rates, symptom expression/complaints, and treatment completion/outcomes. In this study, our objective was to examine the instrument's properties, replicating Keane et al.'s (1988) methodologies, with veterans from World War II, Korean, Vietnam, post-Vietnam, and Persian Gulf (pre- and post-9/11) eras. This retrospective cohort study involved the examination of medical records of 29,280 veterans receiving care across Veterans Affairs medical outpatient centers nationwide. The data revealed significant differences across POS in terms of M-PTSD total scores, F (4, 29,275) = 55.01, p = .000; therefore, analyses were conducted with the entire sample and with each POS. The instrument demonstrated high internal consistency with our sample (α = .92) and across POS (.91 to .92). Receiver operating characteristic curves identified cut-scores ranging from 86 to 112 across the POS with acceptable-to-good sensitivity (68% to 81%) and fair-to-acceptable specificity (61% to 70%), with lower scores among World War II and Korean…