How does the PHQ-9 screen for depression?


Quick Answer

The Patient Health Questionnaire-9, known as PHQ-9, contains nine questions about symptoms of depression that patients can quickly answer during any routine doctor's visit, says the American Family Physician. If the patient's answers suggest the possibility of depression, the physician then administers a full diagnostic interview to see if the patient meets the formal criteria for depression as laid out in the Diagnostic and Statistical Manual of Mental Disorders, 4th Edition.

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Full Answer

In clinical practice, most physicians administer the PHQ-2 as their primary screening tool, according to the American Family Physician. The PHQ-2 asks two questions, one about interest or pleasure in doing things and one about feelings of depression. If the patient answers yes to either question, then the physician administers the PHQ-9 to confirm the finding.

The PHQ-2 has a 97 percent sensitivity and a 67 percent specificity for detecting depression, meaning it catches most cases of depression, but it also falsely categorizes a significant number of nondepressed individuals as depressed, reports the American Family Physician. The PHQ-9 has a 61 percent sensitivity and a 97 percent specificity, which means that a positive finding of depression on the PHQ-9 is almost always correct. When used together, the PHQ-2 identifies practically all depressed individuals, and the PHQ-9 eliminates those falsely diagnosed as depressed by the PHQ-2.

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