The importance of maximal airway response to methacholine in the prediction of asthma development in patients with allergic rhinitis.
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 PC(20) (provocative concentration causing a 20% fall in FEV(1)) 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 (PC(20) < 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 PC(20) (P = 0.123), and the future development of asthma.


CONCLUSIONS
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.
Koh
Y Y
YY
Department of Paediatrics and Clinical Research Institute, Seoul National University Hospital, Seoul, Korea. kohyy@paza.snu.ac.kr
Kang
E K
EK
Min
Y-G
YG
Kim
C K
CK
D000293:Adolescent; D000403:Airway Resistance / Q000187:drug effects* / Q000502:physiology*; D001249:Asthma / Q000150:complications* / Q000453:epidemiology / Q000503:physiopathology*; D001985:Bronchial Provocation Tests; D016085:Bronchoconstrictor Agents / Q000494:pharmacology*; D002648:Child; D002669:Child Welfare; D004305:Dose-Response Relationship, Drug; D005260:Female; D005500:Follow-Up Studies; D005541:Forced Expiratory Volume / Q000187:drug effects / Q000502:physiology; D006801:Humans; D007073:Immunoglobulin E / Q000097:blood / Q000187:drug effects; D007723:Korea / Q000453:epidemiology; D008297:Male; D016210:Methacholine Chloride / Q000494:pharmacology*; D011237:Predictive Value of Tests; D015995:Prevalence; D011446:Prospective Studies; D012221:Rhinitis, Allergic, Perennial / Q000150:complications* / Q000453:epidemiology / Q000503:physiopathology*; D012680:Sensitivity and Specificity; D012882:Skin Tests
D016085:Bronchoconstrictor Agents; D016210:Methacholine Chloride; D007073:Immunoglobulin E