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.