Using the Patient Health Questionnaire‐9 to Measure Depression among Racially and Ethnically Diverse Primary Care Patients

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 Mantel‐Haenszel 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 α 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.