ORIGINAL ARTICLE

Cough, airway inflammation, and mild asthma exacerbation

A B Chang¹, V A Harrhy², J Simpson³, I B Masters⁴, P G Gibson³

¹ Flinders University NT Clinical School, Alice Springs Hospital, Northern Territory
² Department of Respiratory Medicine, Mater Children's Hospital
³ Department of Respiratory and Sleep Medicine, John Hunter Hospital, Newcastle, NSW
⁴ Department of Respiratory Medicine, Royal Children's Hospital, Herston, Queensland

Correspondence to:
Correspondence to:
A/Prof. A B Chang, Flinders University NT Clinical School, Alice Springs Hospital, Northern Territory 0870, Australia;
abchang{at}mac.com

Background: Prospective data on the temporal relation between cough, asthma symptoms, and airway inflammation in childhood asthma is unavailable.

Aims and methods: Using several clinical (diary, quality of life), lung function (FEV₁, FEV₁ variability, airway hyperresponsiveness), cough (diary, cough receptor sensitivity (CRS)), and inflammatory markers (sputum interleukin 8, eosinophilic cationic protein (ECP), myeloperoxidase; and serum ECP) of asthma severity, we prospectively described the course of these markers in children with asthma during a non-acute, acute, and resolution phase. A total of 21 children with asthma underwent these baseline tests; 11 were retested during days 1, 3, 7, and 28 of an exacerbation.

Results: Asthma exacerbations were characterised by increased asthma and cough symptoms and eosinophilic inflammation. Sputum ECP showed the largest increase and peaked later than clinical scores. Asthma scores consistently related to cough score only early in the exacerbation. Neither CRS nor cough scores related to any inflammatory marker.

Conclusion: In mild asthma exacerbations, eosinophilic inflammation is dominant. In asthmatic children who cough as a dominant symptom, cough heralds the onset of an exacerbation and increased eosinophilic inflammation, but cough scores and CRS do not reflect eosinophilic airway inflammation.

Keywords: asthma; cough; sputum; inflammation

Abbreviations: AHR, airway hyperresponsiveness; CRS, cough receptor sensitivity; ECP, eosinophilic cationic protein; ETS, environmental tobacco smoke; FEV₁, forced expiratory volume in one second; FVC, forced vital capacity; HS, hypertonic saline; IL, interleukin; IQR, interquartile range; MPO, myeloperoxidase; QOL, quality of life

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