title: A study of the diagnostic accuracy of the PHQ-9 in primary care elderly.
abstract: BACKGROUND
  The diagnostic accuracy of the Patient Health Questionnaire-9 (PHQ-9) for assessment of depression in elderly persons in primary care settings in the United States has not been previously addressed. Thus, the purpose of this study was to evaluate the test performance of the PHQ-9 for detecting major and minor depression in elderly patients in primary care.
  
  
  METHODS
  A prospective study of diagnostic accuracy was conducted in two primary care, university-based clinics in the Pacific Northwest of the United States. Seventy-one patients aged 65 years or older participated; all completed the PHQ-9 and the 15-item Geriatric Depression Scale (GDS) and underwent the Structured Clinical Interview for Depression (SCID). Sensitivity, specificity, area under the receiver operating characteristic (ROC) curve, and likelihood ratios (LRs) were calculated for the PHQ-9, the PHQ-2, and the 15-item GDS for major depression alone and the combination of major plus minor depression.
  
  
  RESULTS
  Two thirds of participants were female, with a mean age of 78 and two chronic health conditions. Twelve percent met SCID criteria for major depression and 13% minor depression. The PHQ-9 had an area under the curve (AUC) of 0.87 (95% confidence interval [CI], 0.74-1.00) for major depression, while the PHQ-2 and the 15-item GDS each had an AUC of 0.81 (95% CI for PHQ-2, 0.64-0.98, and for 15-item GDS, 0.70-0.91; P = 0.551). For major and minor depression combined, the AUC for the PHQ-9 was 0.85 (95% CI, 0.73-0.96), for the PHQ-2, 0.80 (95% CI, 0.68-0.93), and for the 15-item GDS, 0.71 (95% CI, 0.55-0.87; P = 0.187).
  
  
  CONCLUSIONS
  Based on AUC values, the PHQ-9 performs comparably to the PHQ-2 and the 15-item GDS in identifying depression among primary care elderly.
authors.affiliation: Department of Medicine, Division of Gerontology and Geriatric Medicine, University of Washington, Seattle, WA, USA. phelane@u.washington.edu
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Phelan
authors.forename: Barbara
authors.initials: B
authors.lastname: Williams
authors.forename: Kathryn
authors.initials: K
authors.lastname: Meeker
authors.forename: Katie
authors.initials: K
authors.lastname: Bonn
authors.forename: John
authors.initials: J
authors.lastname: Frederick
authors.forename: James
authors.initials: J
authors.lastname: Logerfo
authors.forename: Mark
authors.initials: M
authors.lastname: Snowden
mesh_terms: D000367:Age Factors; D000368:Aged; D003863:Depression / Q000175:diagnosis* / Q000523:psychology; D003865:Major Depressive Disorder / Q000175:diagnosis* / Q000523:psychology; D005260:Female; D015577:Geriatric Assessment; D006304:Health Status; D006801:Humans; D008297:Male; D011320:Primary Health Care / Q000379:methods*; D011446:Prospective Studies; D011569:Psychiatric Status Rating Scales; D011594:Psychometrics; D012372:ROC Curve; D011795:Surveys and Questionnaires; D014481:United States
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