What makes a difference in exercise-induced bronchoconstriction: an 8 year retrospective analysis.
BACKGROUND
Exercise-induced bronchoconstriction (EIB) was recently classified into EIB alone and EIB with asthma, based on the presence of concurrent asthma.


OBJECTIVE
Differences between EIB alone and EIB with asthma have not been fully described.


METHODS
We retrospectively reviewed who visited an allergy clinic for respiratory symptoms after exercise and underwent exercise bronchial provocation testing. More than a 15% decrease of forced expiratory volume in 1 second (FEV1) from baseline to the end of a 6 min free-running challenge test was interpreted as positive EIB.


RESULTS
EIB was observed in 66.9% of the study subjects (89/133). EIB-positive subjects showed higher positivity to methacholine provocation testing (61.4% vs. 18.9%, p<0.001) compared with EIB-negative subjects. In addition, sputum eosinophilia was more frequently observed in EIB-positive subjects than in EIB-negative subjects (56% vs. 23.5%, p = 0.037). The temperature and relative humidity on exercise test day were significantly related with the EIB-positive rate. Positive EIB status was correlated with both temperature (p = 0.001) and relative humidity (p = 0.038) in the methacholine-negative EIB group while such a correlation was not observed in the methacholine-positive EIB group. In the methacholine-positive EIB group the time to reach a 15% decrease in FEV1 during exercise was significantly shorter than that in the methacholine-negative EIB group (3.2±0.7 min vs. 8.6±1.6 min, p = 0.004).


CONCLUSIONS
EIB alone may be a distinct clinical entity from EIB with asthma. Conditions such as temperature and humidity should be considered when performing exercise tests, especially in subjects with EIB alone.
Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea ; Institute of Allergy and Clinical Immunology, Seoul National University Medical Research Center, Seoul, Korea.
Han-Ki
HK
Park
Institute of Allergy and Clinical Immunology, Seoul National University Medical Research Center, Seoul, Korea ; Department of Internal Medicine, Chung-Ang University College of Medicine, Seoul, Korea.
Jae-Woo
JW
Jung
Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea ; Institute of Allergy and Clinical Immunology, Seoul National University Medical Research Center, Seoul, Korea.
Sang-Heon
SH
Cho
Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea ; Institute of Allergy and Clinical Immunology, Seoul National University Medical Research Center, Seoul, Korea.
Kyung-Up
KU
Min
Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea ; Institute of Allergy and Clinical Immunology, Seoul National University Medical Research Center, Seoul, Korea.
Hye-Ryun
HR
Kang
D000328:Adult; D001249:Asthma / Q000503:physiopathology*; D016535:Bronchial Hyperreactivity / Q000503:physiopathology; D016084:Bronchoconstriction / Q000187:drug effects / Q000502:physiology*; D016085:Bronchoconstrictor Agents / Q000494:pharmacology; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test / Q000379:methods; D005260:Female; D006801:Humans; D006813:Humidity; D008297:Male; D016210:Methacholine Chloride / Q000494:pharmacology; D012189:Retrospective Studies; D013696:Temperature; D055815:Young Adult
D016085:Bronchoconstrictor Agents; D016210:Methacholine Chloride