Individuals struggling with alcohol or substance use have disproportionately high rates of trauma exposure, increasing the likelihood of developing trauma-related psychopathology (Goldstein et al., 2016, Read et al., 2004). In patients diagnosed with a substance use disorder (SUD), rates of co-occurring current posttraumatic stress disorder (PTSD) have been reported as high as 41 % (Read et al., 2004) and lifetime PTSD rates have been reported as high as 52 % (Reynolds et al., 2005). This high co-occurrence rate is worrisome as patients with both disorders are more prone to experiencing a variety of negative health consequences, such as poor treatment adherence, less symptomatic improvement while in treatment, greater legal issues, greater physical health problems, and an increased rate of suicide attempts compared to patients who have a single diagnosis of either disorder (Foa and Williams, 2010, McCauley et al., 2012).

In populations suffering from SUD, PTSD and trauma exposure is infrequently measured and often goes untreated (Ford et al., 2007). However, identifying patients with co-occurring psychiatric conditions is critical to ensure the treatment of both disorders, increasing the likelihood of symptom remission from SUD. Indeed, a recent meta-analysis examining the self-medication hypothesis found that drinking to cope accounted for 80 % of the variance in the relationship between PTSD and harmful alcohol use (Luciano et al., 2022). Patients with unremitted PTSD have been found to demonstrate fewer percent days abstinent following SUD treatment (Read et al., 2004). Importantly, engagement in PTSD treatment has been found to be a significant predictor of remission following treatment (Ouimette et al., 2003, Ouimette et al., 2015). Thus, there is a clear clinical need for systematic screening for PTSD in SUD treatment centers to ensure comprehensive assessment and treatment. The most used PTSD screener in healthcare settings is the PTSD Checklist for DSM-5 (PCL-5). The PCL-5 is a 20-item self-report questionnaire designed to evaluate a probable diagnosis of PTSD (Weathers et al., 2013). While the PCL-5 has been shown to be reliable and valid across various samples (Blevins et al., 2015, Geier et al., 2020, Kagee et al., 2022, Mekawi et al., 2022), shorter screening measures are available and may be a promising addition to standard intake screening with the appeal of a much lower burden on patients.

The Primary Care Posttraumatic Stress Disorder Screen (PC-PTSD) is a strong candidate as a short, reliable PTSD symptom screening measure for use in community-based SUD treatment centers. Research has explored the applicability, diagnostic efficiency, and validity of using the brief PC-PTSD in Veterans Affairs (VA) and civilian substance misusing populations. Developed originally to use in a primary care setting, the PC-PTSD for DSM-IV consists of four yes/no questions representing each PTSD symptom cluster (Prins et al., 2003). This questionnaire has demonstrated potential as a screener for PTSD in SUD samples as it has good diagnostic accuracy, is brief, and is relatively easy to administer. Kimerling and colleagues (2006) found that the PC-PTSD was suitable for detecting PTSD in majority white, male, VA patients with SUD with high sensitivity and specificity using a cut-score of three. The PC-PTSD showed a similarly high sensitivity and moderate specificity when using a cut-score of two in a majority white, male civilian Dutch SUD patient sample (van Dam et al., 2010). Additional support for the use of the PC-PTSD as a screener was found in a majority Black treatment seeking VA SUD sample, with results showing a PC-PTSD cut-score of three demonstrated optimal sensitivity and adequate specificity (Tiet et al., 2013). Most of these samples were found to meet criteria for an alcohol use disorder.

The PC-PTSD has been updated to reflect the diagnostic criteria of PTSD following the DSM-5 and now includes five items (PC-PTSD-5). Primarily, language has been adjusted to ensure participants are responding to subsequent questions about a criterion A traumatic event. The original validation study for the updated measure found that a cut-score of three optimized sensitivity in a majority white male VA sample (Prins et al., 2016). Recently, Bovin and colleagues (Bovin et al., 2021) validated the PC-PTSD-5 in a VA sample and found high levels of diagnostic accuracy, with the optimal cut-score of four for men and three for women. However, the PC-PTSD-5 has not yet been validated in a substance misusing population.

To date, no study has yet validated the PC-PTSD-5 in a socioeconomically disadvantaged, substance misusing community sample. Because of the particularly high rates of PTSD within substance misusing populations, the ability to quickly measure a patients’ trauma symptoms becomes critical for appropriate screening and treatment selection. The PC-PTSD-5 may be a brief alternative to lengthier self-report measures of trauma symptom severity, such as the PCL-5. However, it is crucial to ensure the PC-PTSD-5 performs similarly to the PC-PTSD, a measure previously validated in substance misusing samples. Additionally, the majority of past research in this area has involved veteran populations. Validation in community samples is critical for generalizability. The goal of the current study was to determine the diagnostic accuracy and appropriate cut-score of the PC-PTSD-5 compared to the PCL-5 in a sample of predominantly socioeconomically disadvantaged and minoritized substance misusing trauma-exposed individuals. We hypothesized the PC-PTSD-5 would have good overall diagnostic accuracy in the current sample. Finally, the previous studies outlined above found varying cut-scores; however, the cut-score of three appeared in the majority of studies described. Therefore, we hypothesized a cut-score of three for optimal performance.