Phenotypic differences between asymptomatic airway hyperresponsiveness and remission of asthma

Summary 

Background

The present study aimed to illustrate differences in characteristics and perception of dyspnea between young atopic adults who have no history of asthma (never-asthmatics) with or without asymptomatic airway hyperresponsiveness (AHR) and those who had childhood asthma and consider themselves to be grown out of the disease (past-asthmatics).

Methods

Blood parameters, lung function and methacholine PC₂₀ were measured in 88 never-asthmatics and 24 past-asthmatics. A perception score of dyspnea at 20% fall in FEV₁ (PS₂₀) was obtained by interpolation of the two last points on the perception (modified Borg scale)/fall in FEV₁ curve during methacholine challenge.

Results

Thirty-one of 88 never-asthmatics and eighteen of 24 past-asthmatics exhibited AHR (PC₂₀ was <8 mg/ml). Higher levels of specific IgE to house dust mite in past-asthmatics were observed than never-asthmatics with and without AHR. Mean values of FEV₁ and FEF_25–75 (%predicted) were significantly lower in past-asthmatics than never-asthmatics without AHR, and the values in never-asthmatics with AHR were intermediate between never-asthmatics without AHR and past-asthmatics. PC₂₀ was not significantly different between past-asthmatics and never-asthmatics with AHR. Of particular interest was that PS₂₀ was significantly lower in never-asthmatics with AHR compared with past-asthmatics.

Conclusion

The present findings suggest the possibilities that presence or absence of past history of outgrow of childhood asthma might be associated with airway narrowing, sensitization to house dust mite and perception of dyspnea in young asymptomatic adults with atopy and AHR.

Keywords: Asymptomatic airway hyperresponsiveness (AHR), Bronchial asthma, Clinical remission, Airway narrowing, House dust mites, Perception of dyspnea