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© 2006 American Public Health Association
DOI: 10.2105/AJPH.2006.093310
LETTER |
The authors are with the American Indian and Alaskan Native Programs, School of Medicine, University of Colorado, Denver, and Health Sciences Center, Aurora.
Correspondence: Requests for reprints should be sent to Anne M. Libby, PhD, University of Colorado Health Sciences Center, School of Medicine, Nighthorse Campbell Native Health Building, PO Box 6508, Campus Box F800, Aurora, CO 80045 (e-mail: anne.libby{at}uchsc.edu).
We welcome the opportunity to continue the dialogue on studying American Indians’ experiences with child welfare systems. While Thompson agrees on the importance of such disparities research and a focus on caregivers, he raises an interesting question about the appropriate reference group for racial/ethnic comparisons.
Our decision to use American Indian care-givers as the reference group was hypothesis driven. We were investigating whether disparities exist for American Indian caregivers compared with others in the United States; in the interest of space, we did not report all possible contrasts. However, an interested reader could have examined all comparisons by looking at the results shown in Table 2 of our article. For example, dividing the odds ratio for Whites (2.32) by the odds ratio for Blacks (1.39) results in an odds ratio of 1.67, which is identical to the odds ratio that would have been obtained for the White subgroup if the model had been estimated with Blacks as the reference group. Standard errors, however, cannot be obtained from the table.
Our choice of reference group was also reasonable statistically. We agree that a reference group should be sufficiently large to allow for reasonably precise estimates, as ours did (160/968 unweighted; 20163/308958 weighted). The fact that our estimate for a contrasted subgroup (Hispanics) was statistically significant is evidence that the American Indian group was large enough to act as the reference group.
It is also important to note that changing the reference group does not change the parameter estimates for any other variables in the model or the overall test of the model (here the F statistic). Regardless of the reference group, the precision of parameter estimates for small subgroups may be compromised, as evidenced by standard errors; in our case these were slightly larger for American Indians and Hispanics (proportionally smaller subgroups) than for Whites and Blacks. The issue is thus not which subgroup is the reference group, but small subgroups in general.
Our assertion that "Hispanic caregivers fared the best"1(p630) referred to the fact that, as shown in Table 1, Hispanic caregivers received more assessments and service referrals and had higher rates of prior service receipt than White, Black, and American Indian caregivers.
It is time for disparities research to move beyond rote comparisons with Whites. Rather, we should concentrate on considering and proposing hypotheses to be tested.
Acknowledgments
We thank Jan Beals for her contribution to this response.
References
1. Libby AM, Orton HD, Barth RP, et al. Alcohol, drug, and mental health specialty treatment services and race/ethnicity: a national study of children and families involved with child welfare. Am J Public Health. 2006;96:628–631.
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