Introduction: Depression is common and debilitating, yet treatable; however, it is often overlooked in primary care settings. The second leading cause of disease burden globally, it has significant socioeconomic consequences in Singapore. Hence there is a need for well-validated screening tools to identify depressed patients in primary care. We had previously validated the 9-item Patient Health Questionnaire (PHQ-9) against a structured interview diagnosis of major depressive disorder (Mini International Neuropsychiatric Interview) in 400 patients in a local primary care clinic . The present study was a secondary analysis undertaken to evaluate the performance of 1-and 2-item versions of the PHQ (PHQ-1 and PHQ-2) as compared to the full instrument.

Results: For screening of major depression in local primary care clinic, PHQ-9 shows good validity and reliability. It had sensitivity of 91.7%, specificity of 72.2% (optimal cutoff score 6), with good internal consistency (Cronbach's alpha 0.87). Sensitivity and specificity for PHQ-2 (optimal cutoff score 2) were 91.7% and 66.8% respectively; whereas that for PHQ-1 (optimal cutoff score 1) was 83.3% and 62.9% respectively. For settings where an ultra-brief screen is preferred, PHQ-2 and PHQ-1 may be employed with limitations. Overall prevalence of major depressive disorder in this study was 3.0%.