Diagnostic accuracy of Posttraumatic Stress Disorder Checklist in blast-exposed military personnel.

INTRODUCTION Exposure to psychologically traumatic events is an inherent aspect of military combat deployment and often may lead to posttraumatic stress disorder (PTSD). In Operation Iraqi Freedom (OIF), Operation Enduring Freedom (OEF), and Operation New Dawn (OND), U.S. servicemembers (SMs) have experienced an especially high rate of exposure to blast-induced traumatic events. Heavily used by the insurgents, explosive munitions have accounted for about 78 percent of wounded-in-action cases, the highest proportion for any large-scale conflict [1]. Accordingly, OIF/OEF/OND combatants are typically screened for PTSD after returning from deployment, usually via the easy-to-administer and widely used PTSD Checklist (PCL) [2-3]. The PCL is favored by both the Department of Defense (DoD) and the Veterans Health Administration (VHA) as a PTSD screening tool and is mandated in certain clinical settings. Although not intended as a diagnostic tool, the PCL has been used in numerous published clinical research studies to categorize individuals into PTSD positive versus negative groups, typically using a total score [greater than or equal to] 50 to define PTSD [4]. But most studies, particularly those focusing on mild traumatic brain injury (mTBI) cohorts, have used the PCL in this manner without fully considering its diagnostic accuracy and optimal cut point within their sampled population [5]. The accuracy of any diagnostic tool, such as sensitivity and specificity values, is heavily influenced by the true prevalence of the index condition within the population under study. Regarding PTSD, the entire postdeployment population does not have uniformity of traumatic exposures and risk level. Exposure rates to blast and other traumatic combat events vary widely depending on one's military role and deployment-specific geographic location and missions [6]. Therefore, the true prevalence of PTSD will vary with different sample selection methods, which in turn affects the diagnostic accuracy of the PCL. Therefore, it is unlikely that commonly accepted Veteran population cut points (e.g., 50) [2,7] would be equally appropriate across different population types or study samples. The population of blast-exposed SMs and Veterans is a key target population because they are most at risk for the signature wounds of OIF/OEF/OND, traumatic brain injury (TBI) and PTSD, and are the focal point of Department of Veterans Affairs (VA) and DoD clinical care and research efforts. But the literature lacks guidance on how to use the PCL to categorize PTSD in this very high risk population. Current warfighters and the situations they face are different than those faced by the original validation samples for the PCL (Vietnam and first Gulf war combat Veterans). Now, new stressors may be involved in the development of PTSD--"exponentially" more and much longer deployments, improvised explosive devices and suicide bombers, exposure of peacekeeping forces to combative situations, and higher survivability of wounds [8]. The potential for TBI is also a critical consideration that may confound PTSD determinations within the military and Veteran population. More than 266,000 TBI casualties have been reported by the DoD between 2000 and 2013 [9], and concussion, also known as mTBI, accounts for well over 80 percent of these [10]. Importantly, up to 20 percent of persons sustaining mTBI will develop postconcussion syndrome (PCS), a condition of chronic symptoms and potential psychosocial dysfunction [11-12] that has significant symptom overlap with PTSD. Because of this symptom overlap, the presence of PCS after mTBI may inflate the PCL score and generate higher rates of false positive PTSD screens if standard cut points are used. While PTSD symptoms are reported to occur acutely in up to 40 percent of U.S. military personnel following an mTBI [13] and persistently in 42 percent of recent OIF/OEF Veterans with a history of mTBI [14], the actual PTSD risk and prevalence among those who sustained mTBI during OIF/OEF/OND is unknown because these and other investigations have determined PTSD status from PCL cut points that were derived from much different samples of combat Veterans, notably without high mTBI prevalence. …