Purpose: Our study aimed to validate culturally adapted English and Swahili versions of the Patient Health Questionnaire-9 (PHQ-9) for use with adolescents in Kenya. Criterion validity was determined with clinician-administered diagnostic interviews using the Kiddie Schedule of Affective Disorders and Schizophrenia.

Methods: A total of 250 adolescents comprising 148 (59.2%) females and 102 (40.8%) males aged 10-19 years (mean = 14.76; standard deviation = 2.78) were recruited. The PHQ-9 was administered to all respondents concurrently in English and Swahili. Adolescents were later interviewed by clinicians using Kiddie Schedule of Affective Disorders and Schizophrenia to determine the presence or absence of current symptoms of major depressive disorder. Sensitivity specificity, positive predictive value (PPV) and negative predictive value (NPV), and likelihood ratios for various cut-off scores for PHQ-9 were analyzed using receiver operating characteristic curves.

Results: The internal consistency (Cronbach's α) for PHQ-9 was 0.862 for the English version and 0.834 for Swahili version. The area under the curve was 0.89 (95% confidence interval, 0.84-0.92) and 0.87 (95% confidence interval, 0.82-0.90) for English and Swahili version, respectively, on receiver operating characteristic analysis. A cut-off of ≥ 9 on the English-language version had a sensitivity of 95.0%, specificity of 73.0%, PPV of 0.23, and NPV of 0.99; a cut-off of ≥ 9 on the Swahili version yielded a sensitivity of 89.0%, specificity of 70.0%, PPV of 0.20, and NPV of 0.90.

Discussion: Psychometric properties were comparable across both English-adapted and Swahili-adapted version of the PHQ-9, are reliable, and valid instrument to detect major depressive disorder among adolescents which can be used in resource-limited settings for early identification of adolescents in need of mental health support.