The validity and reliability of the Patient Health Questionnaire-9 for screening depression in primary health care patients in Botswana

BACKGROUND: The lack of locally validated screening instruments contributes to poor detection of depression in primary care. The Patient Health Questionnaire-9 (PHQ-9) is a brief and freely available screening tool which was developed for primary care settings; however, its accuracy may be affected by the population in which it is administered. This study aimed to determine the validity and reliability of PHQ-9 for screening depression in a primary care population in Botswana. METHODS: Data was collected from a conveniently selected sample of 257 adult primary care attendants. The Mini International Neuropsychiatric Interview (MINI) depression module was used as a gold standard to assess criterion validity. RESULTS: Sensitivity and specificity of the PHQ-9 for screening for major depression were 72.4 and 76.3 respectively at a cut off score of nine or more. The area under the ROC curve was 0.808. The PHQ-9 demonstrated good internal consistency with a Cronbach alpha of 0.799. Criterion validity was demonstrated by significant correlation (r = 0.528, p < 0.001) between PHQ-9 and the MINI. Significant negative correlation between PHQ-9 scores and all four domains of the WHO quality of life questionnaire- brief version scores demonstrated good convergent validity. CONCLUSIONS: The PHQ-9 is a reliable and valid instrument to screen for depression in primary care facilities in Botswana. Primary care clinicians in Botswana may use the PHQ-9 to screen for depression with a cut –off score of nine. Further studies should focus on integrating routine depression screening in primary care.