Though atopic and nonatopic asthma have different clinical manifestations, bronchial hyperresponsiveness (BHR) and airway inflammations are common characteristics of them. We investigated BHR to both methacholine and adenosine 5'-monophosphate (AMP), and their relationships with blood eosinophil markers in nonatopic asthma as well as atopic asthma.

We studied 116 children (82 atopics; 34 nonatopics) with mild to moderate asthma. Methacholine and AMP challenge tests were performed and bronchial responsiveness was expressed as PC₂₀ (provocative concentration causing a 20 percent fall in FEV₁); blood eosinopil counts (ETCs) and serum eosinophil cationic protein (ECP) levels were gauged.

In atopics, 95.1 percent and 90.2 percent showed hyperreactivity to methacholine (PC₂₀<16mg/mL) and AMP (PC₂₀<200 mg/mL), respectively. Meanwhile, in nonatopics, 94.1 percent and 52.9 percent displayed hyperreactivity to methacholine and AMP, respectively. The geometric mean of AMP PC₂₀ was lower in atopics (31.6 mg/mL) than in nonatopics (125.9 mg/mL); that of methacholine PC₂₀ was similar in the two groups. AMP PC₂₀ correlated with blood ETCs in both atopics(r=-0.30, P <0.01) and nonatopics (r=-0.57, P <0.01), and correlated with serum ECP levels (r=-0.23, P <0.01) in atopics, but not in nonatopics. Apart from AMP, methacholine PC₂₀ was not associated with blood eosinophil markers in either group.

Atopics more frequently displayed BHR to AMP than nonatopics. Furthermore, BHR to AMP was associated with not only blood ETCs, but serum ECP levels in atopics but was correlated with only blood ETCs in nonatopics. Those results suggest that BHR to AMP reflects airway inflammation in asthma and is more related to atopy.