Validity of the patient health questionnaire-9 for depression screening and diagnosis in East Africa

Depression is often underdiagnosed and undertreated in primary care settings, particularly in developing countries. This is, in part, due to challenges resulting from lack of skilled mental health workers, stigma associated with mental illness, and lack of cross-culturally validated screening instruments. We conducted this study to evaluate the reliability and validity of the Patient Health Questionnaire-9 (PHQ-9) as a screen for diagnosing major depressive disorder among adults in Ethiopia, the second most populous country in sub-Saharan Africa. A total of 926 adults attending outpatient departments in a major referral hospital in Ethiopia participated in this study. We assessed criterion validity and performance characteristics against an independent, blinded, and psychiatrist administered semi-structured Schedules for Clinical Assessment in Neuropsychiatry (SCAN) interview. Overall, the PHQ-9 items showed good internal (Cronbach's alpha=0.81) and test re-test reliability (intraclass correlation coefficient=0.92). A factor analysis confirmed a one-factor structure. Receiver Operating Characteristics (ROC) analysis showed that a PHQ-9 threshold score of 10 offered optimal discriminatory power with respect to diagnosis of major depressive disorder via the clinical interview (sensitivity=86% and specificity=67%). The PHQ-9 appears to be a reliable and valid instrument that may be used to diagnose major depressive disorders among Ethiopian adults.