Methacholine challenge and sputum induction - Reply

AUTHORS’ REPLY We would like to thank Drs
Labiris and Hargreave for their interesting
comments on our article. They have emphasised
the variability in the data and the fact that
the p values for neutrophils and macrophages
were near significance. Moreover, they have
provided the results of a power analysis for
paired continuous data showing that the study
is underpowered to reach solid conclusions.
We agree that their comments are valid
both for the variability of the data and that the
p value was near significance for neutrophils
and macrophages. However, the p value for
eosinophils was far from the significance level
(p = 0.49). This is important because the aim
of the study was to evaluate the influence of
methacholine challenge on overall sputum
cellularity but, in particular, on eosinophils
which are considered the most relevant
inflammatory cell in bronchial asthma.
We are confident that a methacholine inhalation
challenge carried out one hour before
sputum induction in asthmatic subjects does
not alter the eosinophil count in induced
sputum, and that this result is important for
both clinical practice and clinical trials
involving patients with asthma.