Introduction: Depression is common, disabling, and the single most important factor leading to suicide, yet it is underdiagnosed in busy primary care settings. A key challenge facing primary care clinicians in Asia is the selection of instruments to facilitate depression screening. Although the nine-item Patient Health Questionnaire (PHQ-9) and 16-item Quick Inventory of Depressive Symptomatology - Self-Report (QIDS-SR16 ) are used internationally, they have not been directly compared or widely validated in Asian primary care populations. This study aimed to validate the PHQ-9 and QIDS-SR16 against a structured interview diagnosis of Diagnostic and Statistical Manual, 4th Edition, depression based on the Mini-International Neuropsychiatric Interview in a multiethnic Asian sample.
Methods: From April through August 2011, we enrolled 400 English-speaking Singaporean primary care patients. Participants completed a demographic data form, the PHQ-9, and the QIDS-SR16 . They were assessed independently for major and minor depression using the Mini-International Neuropsychiatric Interview.
Results: Sensitivity and specificity for diagnosing major depression were 91.7% and 72.2%, respectively, for the PHQ-9 (optimal cutoff score of 6), and 83.3% and 84.7%, respectively, for the QIDS-SR16 (optimal cutoff score of 9). The QIDS-SR16 also detected minor depression at an optimal cutoff score of 7, with a sensitivity of 94.4% and specificity of 77.9%. The PHQ-9 and QIDS-SR16 showed good internal consistency (Cronbach's α: 0.87 and 0.79, respectively) and good convergent validity (correlation coefficient: r = 0.73, P < 0.001). The overall prevalence of major and minor depressive disorders was 9%.
Discussion: The PHQ-9 and QIDS-SR16 appear to be valid and reliable for depression screening in Asian primary care settings.
Keywords: depression; depressive disorder; primary health care; questionnaire; self-report.
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