Swahili translation and validation of the patient health questionnaire-9 depression scale in the Kenyan head and neck cancer patient population

Background: Depression is an important predictor of post therapy quality of life (QOL) in head and neck (H&N) cancer patients. In addition, depression rates may vary among cultures. Objective: As part of a larger cross cultural study on post therapy QOL differences in H&N cancer patients, the goal of this project was to translate a well-validated English language depression scale into Swahili, and then validate this scale in Kenyan H&N cancer patients. Methods, Settings and Subjects: In Part 1 of the study, we translated the Patient Health Questionnaire-9 (PHQ-9) into Swahili, adhering to established International Quality of Life Association (IQOLA) guidelines. In Part 2, we psychometrically validated the newly translated scale using a prospective study of 48 patients at the Kenyatta National Hospital ENT clinic in Nairobi, Kenya. Results: The Swahili PHQ-9 had good test retest reliability (Intraclass correlation coefficient, 0.71) and internal consistency (Cronbach's alpha = 0.80). It also had good construct validity, as scores correlated strongly with TNM stage (Chi square = 123, p < 0.05), and with the composite and global scores of an H&N cancer specific QOL scale (UW-QOL, r = -0.87, p < 0.05). Conclusion: The Swahili version of the PHQ-9 is a reliable scale in Kenyan H&N cancer patients, and is a valuable tool in screening for and monitoring of depression as a function of QOL in this population.