Understanding recent estimates of PTSD and TBI from Operations Iraqi Freedom and Enduring Freedom

Abstract

As of late summer 2009, some 5,000 U.S. troops had died and 35,000 had been wounded in action during Operation Iraqi Freedom (OIF) and Operation Enduring Freedom (OEF) in Afghanistan. The fraction of wounded troops who survive their injuries is higher than in previous conflicts, such as Vietnam [1-2]. Enhanced survival is a desirable outcome; however, many policy makers and commentators have expressed concerns about the ensuing healthcare needs of wounded servicemembers and veterans. In particular, much attention has recently focused on mild traumatic brain injuries (TBIs), posttraumatic stress disorder (PTSD), and other mental health conditions. Some 80 percent of TBI diagnoses stemming from OIF/OEF have been associated with closed (as opposed to penetrating) head injuries, suggesting that many more TBIs may have gone undiagnosed. (1) Servicemembers who survive gunshot wounds, explosions, or other kinetic events may suffer PTSD but so too may many others who do not receive physical injuries and, again, are not identified. Although individuals who develop PTSD symptoms or sustain mild TBIs (concussions) often regain normal function without treatment, others recover only after medical intervention. To date, no definitive count is available of service-members and veterans who were ever deployed to the conflicts in Iraq or Afghanistan and are impaired by PTSD or TBI. Nonetheless, the specter of large numbers of servicemembers and veterans suffering--undiagnosed and requiring treatment--has been raised by a number of researchers and embraced by the popular press. For an excellent overview of scholarly publications on PTSD and TBI prevalence, see Ramchand et al. [3]. Understanding the scope of these problems helps decision makers effectively allocate scarce healthcare resources; conversely, reliance on incorrect prevalence rates can result in oversupply of medical personnel and equipment in some areas, while other medical services suffer from shortages and excessive waiting times. As recently indicated in an article by Colonel Charles Hoge (Director of the Division of Psychiatry and Neuroscience at Walter Reed Army Institute of Research) and his colleagues, the presage of large numbers of servicemembers with debilitating TBI and PTSD may fuel undesirable clinical and budgetary consequences: unproductive and time-consuming testing, inappropriate treatment and medication, and reinforcement of patients' negative perceptions [4]. There are three main problems with relying on extant studies to estimate the prevalence rates of TBI and PTSD in the full OIF/OEF population. First, the studies generally report the percentage of servicemembers who screen positive for TBI or PTSD, not those who have been diagnosed with the condition by an appropriately trained medical provider. Second, the study samples are not representative of the entire ever-deployed military population. Third, the degree of impairment for servicemembers who have or have had TBI or PTSD is unknown. Although studies often estimate rates of TBI and PTSD with a screening questionnaire, those tools do not replace a clinician-determined diagnosis. For one, screening tools are not comprehensive--typically they do not survey respondents regarding all the symptoms and conditions necessary for a diagnosis. Further, for conditions in which the underlying prevalence in the population is relatively low, screening tools are likely to overestimate the number of cases, particularly when the tool is designed to capture as many potential cases as possible. For example, suppose that 90 percent of people with a certain disease screen positive (sensitivity = 0.90) and 5 percent of those without the disease also screen positive (specificity = 0.95). If the true population prevalence is 10 percent and 1,000 people are screened, a total of 135 people (13.5%) would be expected to test positive: 90 percent of the 100 people (90) who have the disease and 5 percent of the 900 people (45) who do not (false positives). …