Blacks and Exacerbations on LABA vs. Tiotropium (BELT)

Asthma is a chronic respiratory disease that affects over 22 million people in the United States. Asthma produces 500,000 hospital admissions and accounts for 10.1 million days of lost work in adults annually. Asthma has been designated a priority condition of the Effective Health Care Program.

Blacks bear a disproportionate burden of asthma morbidity and mortality. In its 2005 report on ethnic disparities in health care, AHRQ identified hospital admissions for asthma as the second largest disparity in quality of health care for Blacks vs. Caucasians.

Long-acting beta-agonists (LABAs) produce extended increases in airway caliber among patients with asthma via action at the beta2-adrenergic receptor (ADRB2). Adding a LABA to an inhaled corticosteroid controller medication (ICS), can decrease asthma symptoms for many individuals and appears to decrease asthma exacerbations. LABA/ICS has become the most commonly prescribed ICS containing medication.

Drugs acting at ADRB2, including LABAs, have been associated with rare loss of long-term asthma control and increased serious adverse outcomes including death and respiratory failure, even when used with ICS. The risk appears four to five-fold greater in Blacks than non-Black patients with asthma.

Consensus guidelines recommend LABAs be added to ICS in those not completely controlled on ICS alone. These recommendations are based on weighing data on the benefit demonstrated in the general population vs. the rare risk of serious adverse outcomes and balancing the apparent benefits vs. the risks of LABAs (Kramer 2009). However, it appears that LABA/ICS may be significantly less effective in Blacks than Caucasians. Comparison of studies with LABA/ICS in Blacks vs. studies where Blacks were a small minority suggests that Blacks may have much less benefit than other racial groups. Additionally, recent data (Wechsler 2009) suggest that a polymorphism at the 16th position of the ADRB2 gene identifies a group of Blacks (those homozygous for arginine (Arg16Arg)) in whom the response of adding a LABA to an ICS is further diminished. This polymorphism is present in ~20% of US Blacks.