Association between nebuliser therapies adherence and visit-to-visit variability of FEV1 in patients with cystic fibrosis.

At the same level of lung function, some patients with cystic fibrosis have large variations in their FEV1 percent predicted (FEV1pp) values while others have stable values. We hypothesised that lower adherence to nebuliser therapies was associated with higher FEV1pp variability. We conducted a post hoc analysis of the ACtiF trial data. Adherence was calculated using data from data-logging nebulisers, and FEV1pp variability using the coefficient of variation equation. Amongst the 543 patients included in the analysis, those poorly adherent (adherence < 50%) had a higher FEV1pp variability than patients moderately (50 to < 80%) and highly adherent (≥ 80%), with median values (IQR1-3) of 8.1% (4.9-13.7), 6.3% (3.9-9.8), and 6.3% (3.9-9.3) respectively (p < 0.01). This result was confirmed by a multiple linear regression including adherence as a continuous variable (p < 0.01). Further studies are needed to determine the implications of these differences in FEV1pp variability on the prognosis of patients.