Introduction:
Pulmonary function testing (PFT) and specifically forced expiratory
volume in one second (FEV1) is commonly used to monitor
lung disease progression and pulmonary exacerbations (PEx) in patients
with cystic fibrosis (CF)1. While CF patients tend to
have non-reversible obstructive patterns on PFTs2,
reversible obstruction is not uncommon3. Improvement
in FEV1 after inhalation of bronchodilator (BD) in
individuals with CF can be attributed to bronchodilation, improved
mucociliary clearance4–6 and potentially due to
directly modulating function of the cystic fibrosis transmembrane
conductance regulator (CFTR) protein7–9. It can be
speculated that for some individuals with CF, bronchial
hyperresponsiveness or asthma can also contribute to a reversible
pattern of airways obstruction10,11.
A recent American Thoracic Society (ATS)/ European Respiratory Society
(ERS) statement proposed that initial spirometry testing in obstructive
airway diseases should include post BD assessment, and for follow-up
tests, the need for BD testing should be assessed
clinically12. BD responsiveness is a major
characteristic of asthma, and positive acute response to BD defined as a
12% or greater increase in FEV1 helps to confirm this
diagnosis13. Although common in CF as well, the role
of assessing BD responsiveness in different disease settings remains
unclear. Levine et. al. showed that BD response measured in clinically
stable CF patients did not correlate with markers of atopy or clinical
severity, and overall was of limited value3. We
previously demonstrated in pediatric patients with CF that BD testing
does not assist in differentiating allergic bronchopulmonary
aspergillosis (ABPA) from other causes of worsening of lung
function14. Lung function is often monitored during
PEx to evaluate objectively whether patients respond to treatment. In
this study we aimed to assess the clinical value of BD testing performed
during hospital admission for treatment of PEx. Specifically, we aimed
to assess the correlation of BD response with severity of lung disease
prior to PEx and the recovery from PEx. We also aimed to assess whether
CF patients with significant BD response have distinguishable
characteristics from those without BD response.