Relationship between increased airway responsiveness and asthma severity in the childhood asthma management program

The relationship between increased airway responsiveness and asthma severity in children is unclear. The Childhood Asthma Management Program (CAMP) with 1,041 children with mild to moderate asthma offers an opportunity to relate the concentration of methacholine that causes a 20% fall in FEV₁ (PC₂₀) to level of lung function, occurrence of respiratory symptoms, duration of disease, and assessment of severity by clinical staff. Decreasing PC₂₀ was found to be associated with lower levels of lung function (prebronchodilator percent predicted FEV₁: r = 0.29, β = 3.5, p < 0.001), the occurrence of chronic asthma symptoms, persistent wheezing (odds ratio [OR] = 1.66, p < 0.001), subjective clinical staff assessment of asthma severity (p < 0.001), and longer duration of asthma (r = -0.11, β = -0.20, p < 0.002). These data provide evidence that the degree of airway responsiveness is linked to disease severity in children with mild to moderate asthma.