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Monday, December 6, 2010

SARP reports differences in asthma genotypes & phenotypes are race-associated

In this month’s issue, the Severe Asthma Research Program [SARP] presents their findings from a cross-sectional study of the SARP database, which holds clinical, immunological, and physiological data for over 1300 subjects with asthma (Gamble C, Talbott E, Youk A, Holguin F, Pitt B, Silveira L, et al. Racial differences in biologic predictors of severe asthma: Data from the Severe Asthma Research Program. J Allergy Clin Immunol 126;1149-1156.e1). Gamble et al. partition the severe asthma subjects into two categories, “blacks” and “whites” 40 years of age and older, to evaluate variability in asthma presentation. The authors employ a univariable model and a multivariate model to detect in- and between-group differences.

In univariable analyses, higher BMI, reported GERD, and current employment are associated with severe asthma in blacks. Additionally, the presence of 2 or more family members with asthma is positively associated with severe asthma; however, the presence of atopy and 5 or more positive prick skin tests are negatively associated. Whites are more likely to report additional co-morbidities, such as hypertension and diabetes, as well as GERD, and a positive family history of asthma was not significant in whites. Interestingly, owning a pet decreased the risk of severe asthma in whites. Unlike blacks, current employment is not significant in whites with severe asthma. In both blacks and whites, second-hand smoke exposure and serum IgE are not risk factors.

Multivariate models reveal that, unlike the univariable modeling, IgE was strongly associated with severe asthma and a family history of asthma doubled the risk of severe asthma in blacks. Current employment drops out as a risk factor for blacks in this model. Blacks with GERD, high serum IgE, baseline % predicted FEV1, and 2 or more family members with asthma strongly associate with severe asthma. While whites share GERD and baseline % predicted FEV1 as risk factors with blacks, not having a pet, and no family history of asthma predict risk for severe asthma in whites.

Gamble et al. conclude that biologic/genetic factors and family history are equally or more important than socioeconomic factors as in accounting for risk of severe asthma in blacks. We asked the authors about the implications for their study. According to first author, Christy Gamble, DrPHc, MPH, and senior author, Sally Wenzel, MD, “the different predictors for blacks and whites suggest the mechanisms for severe asthma could be different and thus, approaches to treatment of severe asthma in blacks may very well differ from those in whites.”

Do you have any questions for the authors, or comments about this study? We want to hear from you. Please feel free to post your own questions or comments. All questions and comments will be forwarded to the authors for a response.

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