The accuracy of Patient Health Questionnaire-9 in detecting depression and measuring depression severity in high-risk groups in primary care.
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.


METHODS
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).


CONCLUSIONS
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.
Wittkampf
Karin
K
Department of General Practice, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands. k.a.wittkampf@amc.uva.nl
van Ravesteijn
Hiske
H
Baas
Kim
K
van de Hoogen
Henk
H
Schene
Aart
A
Bindels
Patrick
P
Lucassen
Peter
P
van de Lisdonk
Eloy
E
van Weert
Henk
H
D003863:Depression / Q000175:diagnosis* / Q000453:epidemiology; D005260:Female; D006801:Humans; D008297:Male; D008403:Mass Screening; D008875:Middle Aged; D009426:Netherlands / Q000453:epidemiology; D011320:Primary Health Care; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires / Q000592:standards*