(PS13-84) Confirmatory Factor Analysis of the Brief Psychiatric Rating Scale - Expanded in Veterans with Comorbid PTSD and SMI

Introduction: Despite extensive literature that indicates worse functional and clinical outcomes for individuals with PTSD and comorbid severe mental illness (SMI; schizophrenia spectrum, bipolar, and severe and persistent depressive disorders), trauma and PTSD are infrequently assessed and treated in this population (Grubaugh et al., 2011; Seow et al., 2016). This significant research-to-service gap is further compounded by limited efforts to empirically validate standardized PTSD and psychiatric assessments in this vulnerable population (Frueh et al., 2009). The current study sought to address this critical unmet need by validating the factor structure and psychometric properties of the Brief Psychiatric Rating Scale – Expanded (BPRS-E; Lukoff et al., 1986; Thomas et al., 2004) in individuals with PTSD and SMI.

Method: The study sample included 126 Veterans (75.4% Male; 50.8% Black, 42.9% White), ages 22-74 (M_age = 46.4 years; SD = 12.6) with PTSD and co-occurring diagnosis of SMI. Participants were recruited from a PTSD specialty clinic and regional Community Based Outpatient Clinics in the Southeastern United States as part of a larger randomized controlled trial. Confirmatory Factor Analysis (CFA) of the BPRS-E among Veterans with comorbid SMI was conducted to compare the fit of five potential factor structures. Conventional indices of model fit were compared to determine adequacy of each model, and construct validity was evaluated using Pearson correlation coefficients.

Results: The sample presented with “mild” to “moderately ill” psychopathology indicated by an average total BPRS-E score of 36.59 (SD = 9.52; median = 36). Model 2 (12-core items four factor model) emerged as the best fitting model (CFI: 0.944, TLI: 0.924; RMSEA: 0.064 [90% CI: 0030-0.092]; SRMR: 0.061), and the model test statistic was significant (X² = 72.66, df = 48, p = 0.012). All loadings were significant and moderate-to-strong in strength. Model 3 (15-item five factor model) achieved adequate fit, albeit not as strong as Model 2 (CFI: 0.908 TLI: 0.879; RMSEA: 0.071 [90% CI: 0.048-0.092]; SRMR: 0.071; (Χ² = 130.31, df = 80, p = < 0.001). All loadings in Model 3 were significant and adequate-to-strong in size. Models 2 and 3 were not significantly different (X² = 41.17, df = 32, p = 0.129). Construct validity was established via a moderate positive correlation with the HDRS (r = .53; p < .001), as well as low positive correlations with the BDI (r = .34; p < .001) and CAPS (r = .23; p = .004).

Discussion: To our knowledge, this study is the first to confirm the factor structure of the BPRS-E for individuals with PTSD and SMI, wherein the four-factor solution represented the best fitting model. Our results converge with the BPRS consensus model, a four-factor structure validated in numerous other psychiatric populations (Shafer et al., 2005). Notably, no significant differences emerged between the four-factor (Model 2) and five-factor (Model 3) solutions. Yet, Model 3 offers additional interpretation of a fifth factor, disorganization, consistent with more recent analyses (Dazzi et al., 2016; Shafer et al., 2017). In conclusion, our results support the BPRS as a valid diagnostic assessment of psychiatric symptoms among individuals with PTSD and SMI.