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AIDS Care. 2010 Jul;22(7):874-85. doi: 10.1080/09540120903483034.

Measuring depression levels in HIV-infected patients as part of routine clinical care using the nine-item Patient Health Questionnaire (PHQ-9).

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  • 1Department of Medicine, Harborview Medical Center, University of Washington, Seattle, WA, USA.


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.

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