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Queen Elizabeth Children's Service, Royal London Hospital, London, UK
CORRESPONDENCE: S.A. McKenzie, Queen Elizabeth Children's Service, Royal London Hospital, Whitechapel, London, E1 1BB, UK. Fax: 44 2073777325
Keywords: Asthma, atopy, bronchodilating response, wheezing
Received: August 11, 2000
Accepted July 18, 2001
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 510 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 59.9 yrs). Geometric mean baseline Rint was similar in controls and coughers (0.66 and 0.68 kPa·L1·s), but the baseline Rint for wheezers (0.73 kPa·L1·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)·L1, 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.
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