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Measuring Disparities

Bias in the Short Form-36v2 Among Spanish-speaking Medical Patients

Sudano, Joseph J., PhD*,†; Perzynski, Adam, PhD*,†; Love, Thomas E., PhD*,†; Lewis, Steven A., MS*; Murray, Patrick M., MD, MS*,‡; M. Huber, Gail, PT, PhD§; Ruo, Bernice, MD, MAS; Baker, David W., MD, MPH∥,¶

doi: 10.1097/MLR.0b013e31820fb944
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Background Many national surveys have found substantial differences in self-reported overall health between Spanish-speaking Hispanics and other racial/ethnic groups. However, because cultural and language differences may create measurement bias, it is unclear whether observed differences in self-reported overall health reflect true differences in health.

Objectives This study uses a cross-sectional survey to investigate psychometric properties of the Short Form-36v2 for subjects across 4 racial/ethnic and language groups. Multigroup latent variable modeling was used to test increasingly stringent criteria for measurement equivalence.

Subjects Our sample (N=1281) included 383 non-Hispanic whites, 368 non-Hispanic blacks, 206 Hispanics interviewed in English, and 324 Hispanics interviewed in Spanish recruited from outpatient medical clinics in 2 large urban areas.

Results We found weak factorial invariance across the 4 groups. However, there was no evidence for strong factorial invariance. The overall fit of the model was substantially worse (change in Comparative Fit Index >0.02, root mean square error of approximation change >0.003) after requiring equal intercepts across all groups. Further comparisons established that the equality constraints on the intercepts for Spanish-speaking Hispanics were responsible for the decrement to model fit.

Conclusions Observed differences between SF-36v2 scores for Spanish-speaking Hispanics are systematically biased relative to the other 3 groups. The lack of strong invariance suggests the need for caution when comparing SF-36v2 mean scores of Spanish-speaking Hispanics with those of other groups. However, measurement equivalence testing for this study supports correlational or multivariate latent variable analyses of SF-36v2 responses across all the 4 subgroups, as these analyses require only weak factorial invariance.

*Center for Healthcare Research and Policy, Case Western Reserve University at the Metro Health System

Department of Medicine

Department of Physical Medicine and Rehabilitation, School of Medicine, Case Western Reserve University, Cleveland, OH

§Department of Physical Therapy and Human Movement Sciences

Division of General Internal Medicine, Department of Medicine

Institute for Healthcare Studies, Feinberg School of Medicine, Northwestern University, Chicago, IL

Supported by NIH/NIA grant R01-AG022459.

Supplemental Digital Content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal's website (www.lww-medicalcare.com).

Reprints: Joseph J. Sudano, PhD, Center for Health Care Research and Policy Case Western Reserve University at The Metro Health System, 2500 Metro Health Drive R236A, Cleveland, OH E-mail: jsudano@metrohealth.org.

© 2011 Lippincott Williams & Wilkins, Inc.