OBJECTIVE:The Patient Health Questionnaire depression scale (PHQ-9) is a well-validated, Diagnostic and Statistical Manual of Mental Disorders-Fourth Edition (DSM-IV) criterion-based measure for diagnosing depression, assessing severity and monitoring treatment response. The performance of most depression scales including the PHQ-9, however, has not been rigorously evaluated in different racial/ethnic populations. Therefore, we compared the factor structure of the PHQ-9 between different racial/ethnic groups as well as the rates of endorsement and differential item functioning (DIF) of the 9 items of the PHQ-9. The presence of DIF would indicate that responses to an individual item differ significantly between groups, controlling for the level of depression. MEASUREMENTS:A combined dataset from 2 separate studies of 5,053 primary care patients including non-Hispanic white (n =2,520), African American (n =598), Chinese American (n =941), and Latino (n =974) patients was used for our analysis. Exploratory principal components factor analysis was used to derive the factor structure of the PHQ-9 in each of the 4 racial/ethnic groups. A generalized MantelHaenszel statistic was used to test for DIF. RESULTS:One main factor that included all PHQ-9 items was found in each racial/ethnic group with a coefficients ranging from 0.79 to 0.89. Although endorsement rates of individual items were generally similar among the 4 groups, evidence of DIF was found for some items. CONCLUSIONS:Our analyses indicate that in African American, Chinese American, Latino, and non-Hispanic white patient groups the PHQ-9 measures a common concept of depression and can be effective for the detection and monitoring of depression in these diverse populations.

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Functional impairment increased with increasing levels of depression severity in all three racial or ethnic groups, although Latinos consistently reported fewer functional disturbances compared with non-Hispanic whites.

There is a need to improve the detection of mental illness among substance abuse patients and to provide integrated treatment.

The PHQ-9 can be used to screen for depression as well as guide depression treatment planning among Chinese Americans in primary care. Screening for major depression with the PHQ-9 in primary care settings should be considered for appropriate identification and treatment of depression for Chinese-American patients.

Functional impairment increased with increasing levels of depression severity in all three racial or ethnic groups, although Latinos consistently reported fewer functional disturbances compared with non-Hispanic whites.

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