Make the Diagnosis: Posttraumatic Stress Disorder
Prior Probability of Posttraumatic Stress Disorder
In the United States, about 80% of individuals will experience 1 or more traumatic events during their lifetimes.1,2,3 Exposure to trauma is common enough that approximately 8% of US adults may develop posttraumatic stress disorder (PTSD) at some point in their lives, but not all these patients seek healthcare for their symptoms. The prevalence of PTSD in healthcare settings varies depending on the trauma exposure rate of the patient population.4,5,6 Among 20 reviewed studies, the summary lifetime prevalence of PTSD was 13.5%, ranging from 5% in a community primary care population to 35% among women receiving health care at Veterans Health Administration clinics. Thus, 13.5% represents the general prior probability for PTSD among US patients who have experienced trauma, though physicians should adjust this based on their clinic populations.
Population in Whom PTSD Should Be Considered
Patients who have been exposed to a known stressor, such as physical or sexual assault, a natural disaster, a motor vehicle crash, or violence associated with war or civil conflict, should be screened, but the appropriate timing between exposure and screening has not been thoroughly evaluated and some exposed to trauma may have a delayed onset of PTSD. Case finding involves screening patients from populations with high prevalence rates. For example, the US Department of Defense screens all soldiers on deployment and the Department of Veterans Affairs screens all patients. Other high-risk populations include refugees, patients in inner-city clinics, and people in high-risk occupations, such as police officers and firefighters.
Assessing the Likelihood of PTSD
The best studied screening instruments for PTSD are the 4-item Primary Care Posttraumatic Stress Disorder Screen (PC-PTSD) used in Veterans Affairs clinics (at a positive threshold score of ≥ 3) and the 17-item PTSD Checklist (see Table 98-1). Both are self-report instruments that the patient can complete prior to an interview. Both instruments have been clinically validated, and the diagnostic accuracy of the instruments does not seem to vary by clinical setting. The PTSD Checklist has been studied sufficiently to know that the diagnostic accuracy does not vary as a function of the prevalence of disease.
Table 98-1.Useful Findings for Assessing the Likelihood of PTSD ||Download (.pdf) Table 98-1. Useful Findings for Assessing the Likelihood of PTSD
|Screening Tool ||Threshold for Positivity ||LR+ (95% CI) ||LR– (95% CI) |
|PC-PTSD ||≥ 3 ||8.5 (5.6–13) ||0.34 (0.22–0.48) |
|PTSD Checklist ||≥ 38–44 ||6.8 (4.7–9.9) ||0.33 (0.27–0.40) |
The reference standard test is an interview by a professional using the Diagnostic and Statistical Manual of Mental Disorders (5th ...