Bronchodilator responsiveness and atopy in 5-10-yr-old coughers

Abstract

Cough-variant asthma is considered by some to be an asthma phenotype. Bronchodilator responsiveness (BDR) is an undisputed feature of asthma. Of school-aged wheezers, 90% are atopic. Are school-aged coughers who demonstrate BDR also atopic? If so, then it would be reasonable to reserve the diagnosis cough-variant asthma for this particular group. Airway resistance was measured by the interrupter technique (Rint) before and after salbutamol in controls (n=73), coughers (n=63) and previous wheezers (n=63) aged 5-10 yrs. Immunoglobulin (Ig)-E was measured in coughers and wheezers. BDR was expressed as the ratio baseline:post-salbutamol Rint. Groups were of similar age (mean 6.7, range 5-9.9 yrs). Geometric mean baseline Rint was similar in controls and coughers (0.66 and 0.68 kPa x L(-1) x s), but the baseline Rint for wheezers (0.73 kPa x L(-1) s) was greater than that for controls (p=0.05) but not significantly different from coughers (p=0.17). Geometric mean BDR in coughers was 1.22, controls 1.13 and wheezers 1.30 (p=0.01 for coughers and controls; p=0.08 for coughers and wheezers; p<0.001 for controls and wheezers). IgE was lower in coughers than wheezers (geometric means 36 and 364 International Units (IU) x L(-1), p<0.001) and was unrelated to BDR in both groups. In summary, atopy, and not bronchodilator responsiveness, distinguishes groups of coughers from groups of wheezers. A diagnosis of cough-variant asthma cannot be reserved for even those school-aged coughers, who demonstrate bronchodilator responsiveness.