Adaptation and validation of screening measures of anxiety (GAD-7), depression (PHQ-9), and post-traumatic stress disorder (PC-PTSD-5) for use in population-based epidemiological studies in Malawi, Africa

Population-based studies of common mental health conditions (anxiety, depression, post-traumatic stress disorder) require measures that are valid in the study context. We set out to validate the Generalised Anxiety Disorder-7 scale (GAD-7), Patient Health Questionnaire-9 (PHQ-9); and Primary Care PTSD Screen for DSM-5 (PC-PTSD-5) in the most widely spoken languages in Malawi (Chichewa and Chitumbuka). We undertook translation, adaptation, and piloting to produce final versions in both languages. We conducted criterion validation of the GAD-7, PHQ-9 and PC-PTSD-5 against reference diagnoses of DSM-5 generalised anxiety disorder, major/minor depressive episode, and PTSD respectively, using the Structured Clinical Interview for DSM-5 (SCID-5). A weighted sample of screened participants had SCID interview and this was adjusted for in the analysis. We recruited convenience samples of women and men from two sites: a rural Chitumbuka-speaking site where 342 were screened and 219 had SCID; and an urban Chichewa-speaking site where 458 were screened and 251 had SCID. In both languages, the measures had acceptable internal consistency (Cronbach’s alpha ≥ 0.75). Regarding convergent validity, PHQ-9 and GAD-7 were highly correlated but PC-PTSD-5 was only weakly/moderately correlated with the other measures. In Confirmatory Factor Analysis, best fit for GAD-7 and PC-PTSD-5 was a 1-factor structure, and for PHQ-9 was a 2-factor structure; there was only partial measurement invariance between the 2 language versions of each measure. Area under the ROC curve (AUC) for GAD-7 detection of generalised anxiety disorder was: Chitumbuka 0.759 (95%CI: 0.634, 0.871); Chichewa 0.868 (95%CI: 0.812, 0.915). AUC for PHQ-9 detection of major depression was: Chitumbuka 0.634 (95%CI: 0.441, 0.869); Chichewa 0.843 (95%CI: 0.721, 0.927). AUC for PHQ-9 detection of minor-or-major depression was: Chitumbuka 0.751 (95%CI: 0.619, 0.865); Chichewa 0.801 (95%CI: 0.714, 0.879). AUC for PC-PTSD-5 detection of PTSD was: Chitumbuka 0.682 (95%CI: 0.519, 0.853); Chichewa 0.741 (95%CI: 0.604, 0.859). In conclusion, GAD-7 and PHQ-9 showed good/acceptable validity, although criterion validity of PHQ-9 for major depression in Chitumbuka was poor. PC-PTSD-5 showed limitations to its validity, indicating need for further development of PTSD measures in Malawi.