Concordance between PHQ-9 scores and patients’ experiences of depression: a mixed methods study

BACKGROUND: In 2009, a new indicator (DEP 3) was introduced into the Quality and Outcomes Framework. GPs are now encouraged to assess response to antidepressant treatment 5-12 weeks after the initial assessment, to guide clinical decision making. The Patient Health Questionnaire (PHQ-9) is one of the validated instruments that GPs can use to assess the patient's clinical state. AIMS: To explore the extent to which changes in PHQ-9 score over time reflect patients' accounts of their experiences of depression during the same period; and to explore patients' experiences of using the PHQ-9 within primary care consultations. DESIGN OF STUDY: Mixed methods. SETTING: Primary care. METHOD: Patients were recruited through six GP practices. The PHQ-9 and in-depth interviews were used at the same three time points over a 6-month period during a new or first episode of depression. RESULTS: Patterns in the total PHQ-9 score broadly reflected patients' accounts of the severity of their depression over time. However, the PHQ-9 was inaccurate in its assessment of the presence and intensity of thoughts of self-harm, and missed symptoms that are meaningful to patients. At the diagnostic primary care consultation, patients viewed their score as a 'tangible' measure of their condition. Some patients requested the PHQ-9 subsequently as a way to measure their own treatment response and recovery process. CONCLUSION: The potential therapeutic value of the PHQ-9 may be dependent upon the GP's willingness to openly discuss the results and what they may mean for the patient.