The PHQ-9 is effective in screening patients for depression as well as monitoring progress in a variety of situations. This includes patients with chronic disease, such as diabetes and coronary heart disease, but care must be taken in interpretation of the PHQ-9 in these situations because of changes in specificity and sensitivity; however, proper interpretation is possible. Using the PHQ-9 after a pre-assessment with the PHQ-2 increases its specificity, as well as preventing under-diagnosis. Although it is not suitable as a stand-alone tool for diagnosis, it is a cost-effective, efficient method of screening patients in primary care.
Keywords: depression, screening, Patient Health Questionnaire-9, primary care