Prevalence of post-traumatic stress disorder and validity of the Impact of Events Scale – Revised in primary care in Zimbabwe, a non-war-affected African country
Melanie A. Abas,
Monika Müller,
Lorna J. Gibson,
Sarah Derveeuw,
Nirosha Dissanayake,
Patrick Smith,
Ruth Verhey,
Andrea Danese,
Dixon Chibanda
Affiliations
Melanie A. Abas
Centre for Global Mental Health, Institute of Psychiatry, Psychology and Neuroscience, King's College London, UK
Centre for Global Mental Health, Institute of Psychiatry, Psychology and Neuroscience, King's College London, UK; and Clinic for Adult Psychiatry and Psychotherapy, University Hospital of Psychiatry Bern, Switzerland
Lorna J. Gibson
Centre for Global Mental Health, London School of Hygiene and Tropical Medicine, UK
Sarah Derveeuw
Centre for Global Mental Health, Institute of Psychiatry, Psychology and Neuroscience, King's College London, UK
Nirosha Dissanayake
Centre for Global Mental Health, Institute of Psychiatry, Psychology and Neuroscience, King's College London, UK
Patrick Smith
Department of Child and Adolescent Psychiatry, Institute of Psychiatry, Psychology & Neuroscience, King's College London, UK
Department of Child and Adolescent Psychiatry, Institute of Psychiatry, Psychology & Neuroscience, King's College London, UK; Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, Psychology & Neuroscience, King's College London, UK; and National and Specialist CAMHS Clinic for Trauma, Anxiety, and Depression, South London and Maudsley NHS Foundation Trust, UK
Dixon Chibanda
Centre for Global Mental Health, London School of Hygiene and Tropical Medicine, UK; Friendship Bench, Harare, Zimbabwe; and Department of Psychiatry, University of Zimbabwe, Zimbabwe
Background A critical step in research on the epidemiology of post-traumatic stress disorder (PTSD) in low-resource settings is the validation of brief self-reported psychometric tools available in the public domain, such as the Impact Event Scale – Revised (IES-R). Aims We aimed to investigate the validity of the IES-R in a primary healthcare setting in Harare, Zimbabwe. Method We analysed data from a survey of 264 consecutively sampled adults (mean age 38 years; 78% female). We estimated the area under the receiver operating characteristic curve and sensitivity, specificity and likelihood ratios for different cut-off points of the IES-R, against a diagnosis of PTSD made using the Structured Clinical Interview for DSM-IV. We performed factor analysis to evaluate construct validity of the IES-R. Results The prevalence of PTSD was 23.9% (95% CI 18.9–29.5). The area under the curve for the IES-R was 0.90. At a cut-off of ≥47, the sensitivity of the IES-R to detect PTSD was 84.1 (95% CI 72.7–92.1) and specificity was 81.1 (95% CI 75.0–86.3). Positive and negative likelihood ratios were 4.45 and 0.20, respectively. Factor analysis revealed a two-factor solution, with both factors showing good internal consistency (Cronbach's factor-1 α = 0.95, factor-2 α = 0.76). In a post hoc analysis, we found the brief six-item IES-6 also performed well, with an area under the curve of 0.87 and optimal cut-off of 15. Conclusions The IES-R and IES-6 had good psychometric properties and performed well for indicating possible PTSD, but at higher cut-off points than those recommended in the Global North.
