Relationships of Methacholine and Adenosine 5'-Monophosphate Responsiveness with deltaFVC in Children with Allergic Rhinitis

Lee, Jin Hee; Lee, Ju Kyung; Suh, Dong In; Koh, Young Yull

Abstract

PURPOSE
Patients with allergic rhinitis without clinical evidence of asthma often have bronchial hyperresponsiveness (BHR). BHR is commonly assessed by bronchial challenges using direct or indirect stimuli. The percentage decrease in forced vital capacity (FVC) at methacholine PC(20) (deltaFVC) has been proposed as a surrogate marker of the maximal airway response and a useful index of disease severity in asthma. The aim of this study was to compare methacholine and adenosine 5'-monophosphate (AMP) responsiveness with their deltaFVC in children with allergic rhinitis.
METHODS
Eighty-two nonasthmatic children with allergic rhinitis underwent methacholine and AMP bronchial challenge tests. A provocative concentration causing a 20% decline in forced expiratory volume in 1 second (PC(20)) was calculated for each challenge, and the deltaFVC on concentration-response curves in methcholine challenge was analyzed retrospectively.
RESULTS
A positive response to methacholine (methacholine PC(20)<16 mg/mL) was observed in 42.6% (35/82) of patients and the frequency of a positive response to AMP (PC(20)<200 mg/ mL) was 29.2% (24/82). Of these patients, 23 had a methacholine PC(20) above 100 mg/mL and were excluded from the study. Methacholine PC(20) did not correlate significantly with deltaFVC (r=-0.008, P=0.954). However, there was a significant and strong correlation between AMP PC(20) and deltaFVC (r=-0.325, P=0.012).
CONCLUSION
The stronger correlations of deltaFVC for AMP PC(20) than for methacholine PC(20) suggest that the maximal airway response may be better reflected by BHR assessed by AMP than by methacholine in patients with allergic rhinitis.