title: Validation of PHQ-2 and PHQ-9 to screen for major depression in the primary care population.
abstract: OBJECTIVE
  Although screening for unipolar depression is controversial, it is potentially an efficient way to find undetected cases and improve diagnostic acumen. Using a reference standard, we aimed to validate the 2- and 9-question Patient Health Questionnaires (PHQ-2 and PHQ-9) in primary care settings. The PHQ-2 comprises the first 2 questions of the PHQ-9.
  
  
  METHODS
  Consecutive adult patients attending Auckland family practices completed the PHQ-9, after which they completed the Composite International Diagnostic Interview (CIDI) depression reference standard. Sensitivities and specificities for PHQ-2 and PHQ-9 were analyzed.
  
  
  RESULTS
  There were 2,642 patients who completed both the PHQ-9 and the CIDI. Sensitivity and specificity of the PHQ-2 for diagnosing major depression were 86% and 78%, respectively, with a score of 2 or higher and 61% and 92% with a score 3 or higher; for the PHQ-9, they were 74% and 91%, respectively, with a score of 10 or higher. For the PHQ-2 a score of 2 or higher detected more cases of depression than a score of 3 or higher. For the PHQ-9 a score of 10 or higher detected more cases of major depression than the PHQ determination of major depression originally described by Spitzer et al in 1999.
  
  
  CONCLUSIONS
  We report the largest validation study of the PHQ-2 and PHQ-9, compared with a reference standard interview, undertaken in an exclusively primary care population. The PHQ-2 score or 2 or higher had good sensitivity but poor specificity in detecting major depression. Using a PHQ-2 threshold score of 2 or higher rather than 3 or higher resulted in more depressed patients being correctly identified. A PHQ-9 score of 10 or higher appears to detect more depressed patients than the originally described PHQ-9 scoring for major depression.
authors.affiliation: Department of General Practice and Primary Health Care University of Auckland, Auckland, New Zealand. b.arroll@auckland.ac.nz
authors.forename: Bruce
authors.initials: B
authors.lastname: Arroll
authors.forename: Felicity
authors.initials: F
authors.lastname: Goodyear-Smith
authors.forename: Susan
authors.initials: S
authors.lastname: Crengle
authors.forename: Jane
authors.initials: J
authors.lastname: Gunn
authors.forename: Ngaire
authors.initials: N
authors.lastname: Kerse
authors.forename: Tana
authors.initials: T
authors.lastname: Fishman
authors.forename: Karen
authors.initials: K
authors.lastname: Falloon
authors.forename: Simon
authors.initials: S
authors.lastname: Hatcher
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003865:Major Depressive Disorder / Q000175:diagnosis*; D003936:Diagnosis, Computer-Assisted; D005260:Female; D006801:Humans; D008297:Male; D008403:Mass Screening / Q000706:statistics & numerical data*; D008875:Middle Aged; D009520:New Zealand / Q000453:epidemiology; D010821:Physicians, Family / Q000706:statistics & numerical data; D011237:Predictive Value of Tests; D015995:Prevalence; D011320:Primary Health Care / Q000706:statistics & numerical data*; D011594:Psychometrics / Q000706:statistics & numerical data*; D012680:Sensitivity and Specificity; D012984:Software; D011795:Surveys and Questionnaires; D013997:Time Factors; D055815:Young Adult