Airway responsiveness to inhaled aspirin is influenced by airway hyperresponsiveness in asthmatic patients

Abstract

Background/aims: Many patients with aspirin-induced asthma have severe methacholine airway hyperresponsiveness (AHR), suggesting a relationship between aspirin and methacholine in airway response. This study was performed to determine whether methacholine AHR affects the response of asthmatics to inhaled aspirin.

Methods: The clinical records of 207 asthmatic patients who underwent inhalation challenges with both aspirin and methacholine were reviewed retrospectively. An oral aspirin challenge was performed in patients with a negative inhalation response. The bronchial reactivity index (BRindex) was calculated from the percent decrease in lung function divided by the last dose of the stimulus.

Results: Forty-one (20.9%) and 14 (7.1%) patients showed a positive response to aspirin following an inhalation and oral challenge, respectively. Only 24.3 and 14.3% of the responders had a history of aspirin intolerance, respectively. The methacholine BRindex was significantly higher in the inhalation responders (1.46 ± 0.02) than in the oral responders (1.36 ± 0.03, p < 0.01) and in non-responders (n = 141, 1.37 ± 0.01, p < 0.001). The aspirin BRindex was significantly correlated with the methacholine BRindex (r = 0.270, p < 0.001). Three of four patients who received the oral challenge, despite a positive inhalation test, showed negative responses to the oral challenge. Two of these patients had severe AHR.

Conclusions: A considerable number of asthmatic patients with no history of aspirin intolerance responded to the inhalation aspirin challenge. The airway response to aspirin was significantly correlated with methacholine-AHR, and a false-positive response to aspirin inhalation test seemed to occur primarily in patients with severe AHR.

Keywords: Asthma, aspirin-induced; Bronchial reactivity; Methacholine.

Figure 1

The methacholine-PC20 (A) and BRindex (B) for patients with asthma classified according to their responses to the inhalation and oral aspirin challenges. PC20, the provocative concentration of methacholine that resulted in a 20% decrease in the forced expiratory volume in one second (FEV1); BRindex, the bronchial reactivity index calculated using the equation: log10 (10 + maximal % fall in FEV1 / log10 [dose in mg/dL of methacholine required to produce the response]). ^aPositive response to inhalation aspirin challenge. ^bPositive response to oral aspirin challenge. ^cNegative response to both inhalation and oral aspirin challenges.

Figure 2

Distribution of the severity of methacholine airway hyperresponsiveness (AHR) in patients with asthma, classified according to their responses to the inhalation and oral aspirin challenges. The values of the provocative concentration of methacholine that resulted in a 20% decrease in the forced expiratory volume in one second (PC20) were divided as follows: severe, PC20 < 0.2; moderate, PC20 = 0.2 to 2.0; mild, PC20 = 2.0 to 16; and normal, PC20 > 16 mg/mL. ^aPositive response to inhalation aspirin challenge. ^bPositive response to oral aspirin challenge. ^cNegative response to both inhalation and oral aspirin challenges.

Figure 3

Relationship of airway responsiveness between the aspirin and methacholine bronchial reactivity index (BRindex), calculated using the equation: log10 (10 + maximal % fall in FEV1 / log10 [dose in mg/dL of stimulus required to produce the response]).