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Keywords:

  • allergic rhinitis;
  • asthma;
  • airway hyper-responsiveness;
  • methacholine;
  • maximal airway response;
  • PC20

Summary

Background Allergic rhinitis is a known predictor and correlate of asthma incidence. However, it is not clear which patients with allergic rhinitis are at greater risk of the development of asthma.

Objective The aim of this study was to investigate whether airway hypersensitivity and/or increased maximal response on the dose–response curve to methacholine would predict the development of asthma in subjects with allergic rhinitis.

Methods One hundred and forty-one children with allergic rhinitis were prospectively studied for 7 years. At the initiation of the study, bronchial provocation test with methacholine using a stepwise increasing concentration technique was performed to measure PC20 (provocative concentration causing a 20% fall in FEV1) and maximal response. Each subject was evaluated at least every 6 months and details of asthmatic symptoms or signs experienced during the intervening period were taken.

Results Twenty of 122 subjects available for the follow-up developed asthma. Nine (19.6%) of 46 hypersensitive (PC20 < 18 mg/mL) subjects developed asthma, compared with 11 (14.5%) of 76 normosensitive subjects (P = 0.462). Eight (32%) of 25 subjects without maximal response plateau developed asthma, compared with 12 (12.4%) of 97 subjects with maximal response plateau (P = 0.018). Score test for trend revealed a significant association between the level of maximal response (P = 0.007), but not the degree of methacholine PC20 (P = 0.123), and the future development of asthma.

Conclusion An increased maximal airway response to methacholine is shown to be a better predictor for the future development of asthma in patients with allergic rhinitis, than airway hypersensitivity to methacholine.