Study results indicate that African-American patients with asthma appear to exhibit greater eosinophilic airway inflammation than their Caucasian cohorts, possibly explaining the greater asthma burden seen among the former population.
With study data indicating that airway inflammation is a key component of asthma that, when uncontrolled, leads to asthma exacerbations, innovations in asthma treatment are becoming more personalized and based on airway inflammation type. Prior research also suggests that African-American patients are two to three times more likely to experience asthma-related hospitalizations, emergency department visits, or mortality when compared with Caucasians. And while emerging evidence suggests that differences in airway inflammation can affect treatment response, whether the patterns of airway inflammation vary across race has been unclear. “While we are entering an age of personalized medicine in asthma, there are still gaps in our knowledge of the best medicines to treat asthma in African Americans,” says Sharmilee M. Nyenhuis, MD.
For a study published in The Journal of Allergy and Clinical Immunology, Dr. Nyenhuis, and colleagues set out to determine if differences exist in the prevalence of eosinophilic versus non-eosinophilic airway inflammatory phenotypes in African-American versus Caucasian patients with asthma. “Because inhaled steroids can modify airway inflammation, we analyzed patients taking inhaled steroids separately,” says Dr. Nyenhuis. “We performed a secondary analysis of self-identified African Americans and Caucasians with asthma enrolled in clinical trials conducted by the National Heart, Lung, and Blood Institute-sponsored Asthma Clinical Research Network and AsthmaNet.”
Demographics, clinical characteristics, and sputum cytology after sputum induction were examined in more than 1,000 patients. The researchers used a sputum eosinophil 2% cut point to define subjects with either an eosinophilic (≥2%) or noneosinophilic (<2%) inflammatory phenotype. All participants were aged 12 or older; met the criteria for mild or moderate persistent asthma as defined by the National Asthma Education and Prevention Program Guidelines for the Diagnosis and Management of Asthma, were current nonsmokers with a lifetime history of smoking no greater than 10 pack years, and had not smoked within the past 12 months.
African-American participants had a lower forced expiratory volume in one second percent predicted (80% vs 85%), greater total immunoglobulin E levels (197 Iu/mL vs 120 Iu/mL), and a greater proportion with uncontrolled asthma (43% vs 28%) when compared with Caucasian participants. Overall, no significant differences in eosinophilic airway inflammation were observed between African-American and Caucasian patients regardless of whether or not they were taking inhaled corticosteroids (ICS). However, after adjusting for confounding factors, African-American patients taking inhaled corticosteroids were more likely to have persistent eosinophilic airway inflammation, explains Dr. Nyenhuis (Figure). “This chronic inflammation may contribute to the greater burden of asthma in African Americans when compared with Caucasians,” she adds.
When assessing the frequency of eosinophilic airway inflammation in participants who had two sputum samples, Dr. Nyenhuis and colleagues found that eosinophilic inflammation may be present only intermittently. “Thus, if it is not present when first measured, clinicians should consider assessing the inflammatory phenotype again in the future,” she says.
While there are many factors—including social, biologic, and environmental—that contribute to a greater proportion of African-American patients having uncontrolled asthma when compared with Caucasians, according to Dr. Nyenhuis, she speculates that the persistence of eosinophilic airway inflammation in African Americans may be associated with asthma exacerbations and an impaired response to ICS.
“Our findings provide preliminary rationale that African-American patients with eosinophilic airway inflammation may not benefit from increasingly strong ICS treatment,” Dr. Nyenhuis says, “and that physicians may want to consider other targeted therapies for eosinophilic asthma in African-American patients who continue to have uncontrolled asthma.”