Factors predicting inhaled corticosteroid responsiveness in African American patients with asthma.

BACKGROUND: African American patients disproportionately experience uncontrolled asthma. Treatment with an inhaled corticosteroid (ICS) is considered first-line therapy for persistent asthma. OBJECTIVE: We sought to determine the degree to which African American patients respond to ICS medication and whether the level of response is influenced by other factors, including genetic ancestry. METHODS: Patients aged 12 to 56 years who received care from a large health system in southeast Michigan and who resided in Detroit were recruited to participate if they had a diagnosis of asthma. Patients were treated with 6 weeks of inhaled beclomethasone dipropionate, and pulmonary function was remeasured after treatment. Ancestry was determined by genotyping ancestry-informative markers. The main outcome measure was ICS responsiveness defined as the change in prebronchodilator FEV(1) over the 6-week course of treatment. RESULTS: Among 147 participating African American patients with asthma, average improvement in FEV(1) after 6 weeks of ICS treatment was 11.6%. The mean proportion of African ancestry in this group was 78.4%. The degree of baseline bronchodilator reversibility was the only factor consistently associated with ICS responsiveness, as measured by both an improvement in FEV(1) and patient-reported asthma control (P = .001 and P = .021, respectively). The proportion of African ancestry was not significantly associated with ICS responsiveness. CONCLUSIONS: Although baseline pulmonary function parameters appear to be associated with the likelihood to respond to ICS treatment, the proportion of genetic African ancestry does not. This study suggests that genetic ancestry might not contribute to differences in ICS controller response among African American patients with asthma.

Dual-specificity phosphatase 1 as a pharmacogenetic modifier of inhaled steroid response among asthmatic patients.

BACKGROUND: Inhaled corticosteroids (ICSs) are considered first-line treatment for persistent asthma, yet there is significant variability in treatment response. Dual-specificity phosphatase 1 (DUSP1) appears to mediate the anti-inflammatory action of corticosteroids. OBJECTIVE: We sought to determine whether variants in the DUSP1 gene are associated with clinical response to ICS treatment. METHODS: Study participants with asthma were drawn from the following multiethnic cohorts: the Genetics of Asthma in Latino Americans (GALA) study; the Study of African Americans, Asthma, Genes & Environments (SAGE); and the Study of Asthma Phenotypes and Pharmacogenomic Interactions by Race-ethnicity (SAPPHIRE). We screened GALA study participants for genetic variants that modified the relationship between ICS use and bronchodilator response. We then replicated our findings in SAGE and SAPPHIRE participants. In a group of SAPPHIRE participants treated with ICSs for 6 weeks, we examined whether a DUSP1 polymorphism was associated with changes in FEV(1) and self-reported asthma control. RESULTS: The DUSP1 polymorphisms rs881152 and rs34507926 localized to different haplotype blocks and appeared to significantly modify the relationship between ICS use and bronchodilator response among GALA study participants. This interaction was also seen for rs881152 among SAPPHIRE but not SAGE participants. Among the group of SAPPHIRE participants prospectively treated with ICSs for 6 weeks, rs881152 genotype was significantly associated with changes in self-reported asthma control but not FEV(1). CONCLUSION: DUSP1 polymorphisms were associated with clinical response to ICS therapy and therefore might be useful in the future to identify asthmatic patients more likely to respond to this controller treatment.