Diagnostic Validity of Patient Health Questionnaire-9 and Composite International Diagnostic Interview Assessment Scales for Depression in East Africa

Thesis (Ph.D.)--University of Washington, 2013 Background: Depression is one of the leading causes of disability and largest contributor to the global burden of disease. In sub-Saharan Africa, depression often goes undetected and untreated, in part, due to a lack of validated screening and diagnostic instruments. Therefore, we conducted a validation study of the Patient Health Questionnaire (PHQ-9) and fully structured Composite International Diagnostic Interview (CIDI) in diagnosing current major depressive disorder (MDD) among Ethiopian adults. Methods: A total of 926 adults attending outpatient departments in a major referral hospital in Addis Ababa, Ethiopia participated in this study. We used a two stage-study design where participants were first interviewed using an Amharic versions of PHQ-9 and the CIDI instruments and then a stratified random sample underwent a follow-up semi-structured clinical interview conducted by a psychiatrist, blinded to the screening results, using Schedules for Clinical Assessment in Neuropsychiatry (SCAN) instrument. We tested construct validity using factor analysis and by examining associations of PHQ-9/CIDI with self-reported quality of life as assessed using the World Health Organization Quality of Life (WHO-QOL) Questionnaire. We calculated the psychometric properties of the PHQ-9/CIDI using the SCAN diagnostic interview as a gold standard. Results: Our study provided evidence for unidimensionality of core depression screening questions on both PHQ-9 and CIDI interviews with good factor loadings on a major core depressive factor. The PHQ-9 items showed good internal (Cronbach's alpha=0.85) and test re-test reliability (intraclass correlation coefficient=0.92). Similarly, we found that the CIDI diagnostic interview has good internal reliability (Cronbach's alpha= 0.97) among Ethiopian adults. Quality of life, as reflected in subscale scores for four WHO-QOL domains, was significantly lower among adults classified as depressed on the PHQ-9 and CIDI compared to those classified as not depressed. Receiver Operating Characteristics analysis showed that a PHQ-9 threshold score of 9 offered the optimal discriminatory power with respect to diagnosis of major depressive disorder via the clinical interview (sensitivity= 79% and specificity= 72%). Compared to the SCAN reference standard, the CIDI had fair specificity (72.2%) but low sensitivity (51.0%). Conclusion: The PHQ-9 is a reliable and valid instrument that may be used as a screen for major depressive disorder among Ethiopian adults in outpatient health care settings. The CIDI had fair specificity and low sensitivity in detecting MDD compared with psychiatrist administered SCAN diagnosis. Our findings are generally consistent with prior studies. Use of fully structured interviews such as the CIDI for MDD diagnosis in clinical settings might lead to under detection of MDD