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Letters to the Editor

In Reply to Tennermann

Hsu, Paul MPH, PhD

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doi: 10.1097/ACM.0000000000003081
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I thank Tennermann for her comments on the Invited Commentary I coauthored. I absolutely agree with her statement that “there is nothing ambiguous about the multiracial/multiethnic experience in the United States,” and it was never my author team’s intent to minimize the tremendous diversity of this population. Our purpose was to draw attention to a large and growing population whose very existence challenges the use of race/ethnic (R/E) categories as research constructs to predict health outcomes. If half of California’s babies fall outside the boundaries of the Office of Management and Budget’s R/E constructs, the internal validity of their use has to be seriously questioned. Our work simply pointed out the methodological inadequacies of the current R/E classifications. We are not at all attempting to create yet another category— the “racially ambiguous”—but are using the existence of ambiguity to highlight the limitations of utilizing R/E categories in health disparities research.

In epidemiology, “temporal ambiguity” is used to describe situations when it is unclear whether a particular exposure or risk factor has occurred prior to a particular disease or outcome.1 (For example, cross-sectional and ecologic studies are often prone to “temporal ambiguity.”) In engineering, the “spatial ambiguity function” is a potential tool for signal processing when there are direction finding and/or source signal separation problems.2 It is in this research sense that we use the term “racial ambiguity.”

We recognize that labels matter, and we welcome the input of researchers, policymakers, and all interested stakeholders. We strongly support the right of all individuals to self-identify and choose their own narrative, for that has not always been the case. We seek collaborative and collegial discussions of the appropriate ways to conceptualize the diversity that this increasing demographic suggests. The goal is to work together to reduce the very health disparities that have often resulted from bias and discrimination.

Paul Hsu, MPH, PhD
Adjunct assistant professor, Department of Medicine, David Geffen School of Medicine at UCLA, Los Angeles, California;


1. Rothman KJ, Greenland S, Lash TL. Modern Epidemiology, 2008.3rd ed. Philadelphia, PA: Lippincott Williams & Wilkins.
2. Amin MG, Belouchrani A, Zhang Y. The spatial ambiguity function and its applications. IEEE Signal Process Lett. 2000;7:138–140.
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