title: Measuring depression levels in HIV-infected patients as part of routine clinical care using the nine-item Patient Health Questionnaire (PHQ-9).
abstract: Little is known about the psychometric properties of depression instruments among persons infected with HIV. We analyzed data from a large sample of patients in usual care in two US cities (n=1467) using the nine-item Patient Health Questionnaire (PHQ-9) from the PRIME-MD. The PHQ-9 had curvilinear scaling properties and varying levels of measurement precision along the continuum of depression measured by the instrument. In our cohort, the scale showed a prominent floor effect and a distribution of scores across depression severity levels. Three items had differential item functioning (DIF) with respect to race (African-American vs. white); two had DIF with respect to sex; and one had DIF with respect to age. There was minimal individual-level DIF impact. Twenty percent of the difference in mean depression levels between African-Americans and whites was due to DIF. While standard scores for the PHQ-9 may be appropriate for use with individual HIV-infected patients in cross-sectional settings, these results suggest that investigations of depression across groups and within patients across time may require a more sophisticated analytic framework.
authors.affiliation: Department of Medicine, Harborview Medical Center, University of Washington, Seattle, WA, USA. pcrane@u.washington.edu
authors.forename: P K
authors.initials: PK
authors.lastname: Crane
authors.forename: L E
authors.initials: LE
authors.lastname: Gibbons
authors.forename: J H
authors.initials: JH
authors.lastname: Willig
authors.forename: M J
authors.initials: MJ
authors.lastname: Mugavero
authors.forename: S T
authors.initials: ST
authors.lastname: Lawrence
authors.forename: J E
authors.initials: JE
authors.lastname: Schumacher
authors.forename: M S
authors.initials: MS
authors.lastname: Saag
authors.forename: M M
authors.initials: MM
authors.lastname: Kitahata
authors.forename: H M
authors.initials: HM
authors.lastname: Crane
mesh_terms: D000328:Adult; D003430:Cross-Sectional Studies; D003866:Depressive Disorder / Q000175:diagnosis*; D005260:Female; D015658:HIV Infections / Q000523:psychology*; D006801:Humans; D008297:Male; D008603:Mental Health; D008875:Middle Aged; D011594:Psychometrics; D011795:Surveys and Questionnaires; D055815:Young Adult