Monitoring depression treatment outcomes with the patient health questionnaire-9

• Published in: Medical care Vol. 42; no. 12; p. 1194
• Main Authors: Löwe, Bernd, Unützer, Jürgen, Callahan, Christopher M, Perkins, Anthony J, Kroenke, Kurt
• Format: Journal Article
• Language: English
• Published: United States 01.12.2004
• Subjects: Aged; Depressive Disorder, Major - diagnosis; Depressive Disorder, Major - therapy; Diagnostic and Statistical Manual of Mental Disorders; Dysthymic Disorder - diagnosis; Dysthymic Disorder - therapy; Female; Humans; Interview, Psychological; Male; Outcome Assessment (Health Care) - methods; Primary Health Care - standards; Psychiatric Status Rating Scales; Psychometrics - instrumentation; Quality of Life - psychology; Self Efficacy; Sickness Impact Profile; Surveys and Questionnaires
• ISSN: 0025-7079
• DOI: 10.1097/00005650-200412000-00006

Although effective treatment of depressed patients requires regular follow-up contacts and symptom monitoring, an efficient method for assessing treatment outcome is lacking. We investigated responsiveness to treatment, reproducibility, and minimal clinically important difference of the Patient Health Questionnaire-9 (PHQ-9), a standard instrument for diagnosing depression in primary care. This study included 434 intervention subjects from the IMPACT study, a multisite treatment trial of late-life depression (63% female, mean age 71 years). Changes in PHQ-9 scores over the course of time were evaluated with respect to change scores of the SCL-20 depression scale as well as 2 independent structured diagnostic interviews for depression during a 6-month period. Test-retest reliability and minimal clinically important difference were assessed in 2 subgroups of patients who completed the PHQ-9 twice exactly 7 days apart. The PHQ-9 responsiveness as measured by effect size was significantly greater than the SCL-20 at 3 months (-1.3 versus -0.9) and equivalent at 6 months (-1.3 versus -1.2). With respect to structured diagnostic interviews, both the PHQ-9 and the SCL-20 change scores accurately discriminated patients with persistent major depression, partial remission, and full remission. Test-retest reliability of the PHQ-9 was excellent, and its minimal clinically important difference for individual change, estimated as 2 standard errors of measurement, was 5 points on the 0 to 27 point PHQ-9 scale. Well-validated as a diagnostic measure, the PHQ-9 has now proven to be a responsive and reliable measure of depression treatment outcomes. Its responsiveness to treatment coupled with its brevity makes the PHQ-9 an attractive tool for gauging response to treatment in individual patient care as well as in clinical research.