Testing for intersectional measurement invariance with the alignment method: Evaluation of the 8-item patient health questionnaire

Objective: To demonstrate the use of the alignment method to evaluate whether surveys function similarly (i.e., have evidence of measurement invariance) across culturally diverse intersectional groups. Intersectionality theory recognizes the interconnected nature of social categories such as race, gender, ethnicity, and socioeconomic status. Data Sources: A total of 30,215 American adult's responses to the eight-item Patient Health Questionnaire depression assessment scale (PHQ-8) from the 2019 National Health Interview Survey (NHIS). Study Design: Using the alignment method, we examined the measurement invariance (equivalence) of the PHQ-8 depression assessment scale across 16 intersectional subgroups defined at the intersection of age (under 52, 52 and older), gender (male, female), race (Black, non-Black), and education (no bachelor's degree, bachelor's degree). Principal Findings: Overall, 24% of the factor loadings and 5% of the item intercepts showed evidence of differential functioning across one or more of the intersectional groups. These levels fall beneath the benchmark of 25% suggested for determining measurement invariance with the alignment method. Conclusions: The results of the alignment study suggest that the PHQ-8 functions similarly across the intersectional groups examined, despite some evidence of different factor loadings and item intercepts in some groups (i.e., noninvariance). By examining measurement invariance through an intersectional lens, researchers can investigate how a person's multiple identities and social positions possibly contribute to their response behavior on an assessment scale. KEYWORDS evaluation design and research, gender/sex differences in health and health care, health equity, psychometrics, racial/ethnic differences in health and health care What is known on this topic * Intersectionality is a theoretical and analytic framework for understanding how multiple social and political factors (e.g., gender or race) intersect to affect an individual's lived experience. * Measurement invariance means that a scale functions similarly across groups, contexts, or measurement occasions. * No prior research has evaluated the measurement invariance of the widely used eight-item Patient Health Questionnaire depression scale (PHQ-8) across intersectional groups. What this study adds * Our research provides an empirical example of using the multiple-group factor analysis alignment method to evaluate the intersectional measurement invariance of a scale. * Because less than 25% of the factor loadings and intercepts were noninvariant, considered a benchmark for evaluating measurement invariance with the alignment method, the PHQ-8 appears to function similarly across culturally diverse groups defined at the intersection of age, education, gender, and race.
Researchers often compare scale means across groups. However, comparing scale means is only appropriate if the scale measures the same construct (i.e., factor) in the same way across groups. Measurement [...]