African Americans May Have Impaired Response to Corticosteroids
African Americans are more likely to have eosinophilic airway inflammation than are whites, despite taking higher doses of asthma medications such as inhaled corticosteroids, according to a new study.
“This finding may help explain the higher rate of uncontrolled asthma in African Americans and suggests that African Americans may have an impaired response to corticosteroids,” said study lead author Sharmilee M. Nyenhuis, MD, assistant professor of medicine at the University of Illinois at Chicago College of Medicine.
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The researchers performed a secondary analysis of self-identified African American and white subjects with asthma enrolled in clinical trials conducted by the National Heart, Lung, and Blood Institute-sponsored Asthma Clinical Research Network and AsthmaNet. They examined demographics, clinical characteristics, and sputum cytology after sputum induction and used a sputum eosinophil 2% cut point to define subjects with either an eosinophilic (≥2%) or noneosinophilic (<2%) inflammatory phenotype.
Among 1018 participants, African American subjects (n=264) had a lower FEV1 percent predicted (80% vs 85%), greater total immunoglobulin E levels (197 vs 120 IU/mL), and a greater proportion with uncontrolled asthma (43% vs 28%) compared with white subjects (n=754). The study included 922 subjects treated with inhaled corticosteroids (ICS+) (248 African American and 674 white subjects) and 298 subjects not treated with inhaled corticosteroids (ICS–) (49 African American and 249 white subjects).
The investigators found eosinophilic airway inflammation not significantly different between African American and white subjects in either group (percentage with eosinophilic phenotype: ICS+ group, 19% vs 16%; ICS– group, 39% vs 35%, respectively). However, when adjusted for confounding factors, African American subjects were more likely to exhibit eosinophilic airway inflammation than white subjects in the ICS+ group (odds ratio, 1.58; 95% CI, 1.01-2.48) but not in the ICS– group.
“African-American patients with asthma, who are on inhaled corticosteroids and whose asthma is not well controlled, may not benefit from increasingly strong corticosteroid treatment and may need other targeted therapies for eosinophilic asthma,” Dr Nyenhuis said.
African Americans had a higher body mass index than did whites, which may contribute to the poor response to asthma treatment seen in the study, she said. Efforts directed at obesity prevention and weight loss may help reduce race-related asthma disparities but need further study.
“There is an ongoing study by AsthmaNet, the asthma clinical trials network, to evaluate the best add-on treatment option in African Americans with asthma that will begin to address some of the knowledge gaps raised from this study,” Dr Nyenhuis said.
—Mike Bederka
Reference:
Nyenhuis SM, Krishnan JA, Berry A, et al. Race is associated with differences in airway inflammation in patients with asthma [published online December 31, 2016]. J Allergy Clin Immunol. doi:10.1016/j.jaci.2016.10.024.