Abstract
Objective: Only half of patients with depressive disorder are diagnosed by their family physicians. Screening in high-risk groups might reduce this hidden morbidity. This study aims to determine the accuracy of the Patient Health Questionnaire-9 (PHQ-9) in (a) screening for depressive disorder, (b) diagnosing depressive disorder and (c) measuring the severity of depressive disorder in groups that are at high risk for depressive disorder. Method: We compared the performance of the PHQ-9 as a screening instrument and as a diagnostic instrument to that of the Structured Clinical Interview for DSM-IV Axis I Disorders (SCID-I) interview, which we used as reference standard. Three high-risk groups of patients were selected: (a) frequent attenders, (b) patients with mental health problems and (c) patients with unexplained complaints. Patients completed the PHQ-9. Next, patients who were at risk for depression (based on PHQ scores) and a random sample of 20% of patients who were not at risk were selected for a second PHQ-9 and the reference standard (SCID-I). We assessed the adequacy of the PHQ-9 as a tool for severity measurement by comparing PHQ-9 scores with scores on the 17-item Hamilton Depression Rating Scale (HDRS-17) in patients diagnosed with a depressive disorder. Results: Among 440 patients, both PHQ-9 and SCID-I were analyzed. The test characteristics for screening were sensitivity=0.93 and specificity=0.85; those for diagnosing were sensitivity=0.68 and specificity=0.95. The positive likelihood ratio for diagnosing was 14.2. The HDRS-17 was administered in 49 patients with depressive disorder. The Pearson correlation coefficient of the PHQ-9 to the HDRS-17 was r=.52 (P<.01). Conclusion: The PHQ-9 performs well as a screening instrument, but in diagnosing depressive disorder, a formal diagnostic process following the PHQ-9 remains imperative. The PHQ-9 does not seem adequate for measuring severity.
| Original language | English |
|---|---|
| Pages (from-to) | 451-459 |
| Number of pages | 9 |
| Journal | General Hospital Psychiatry |
| Volume | 31 |
| Issue number | 5 |
| DOIs | |
| Publication status | Published - Sept 2009 |
| Externally published | Yes |
Bibliographical note
Funding Information:We are grateful for the work and support of Judith Kosman. We would like to thank the participating FPs and patients. This study was funded by The Netherlands Organization for Health Research and Development (ZonMw) Mental Health Program (nos. 100.003.005 and 100.002.021) and the Academic Medical Center/University of Amsterdam.
