RESUMO
RATIONALE: Declines in percent predicted Forced Expiratory Volume in 1 Second (ppFEV1) are an important marker of clinical progression of Cystic Fibrosis (CF). OBJECTIVES: We examined ppFEV1 variability on a combined outcome of lung transplant or death. METHODS: We estimated the association between ppFEV1 variability and the combined outcome of lung transplant or death. We included children ages 8 years and above with CF and two prior years of ppFEV1 data before baseline between 2005 and 2021. We defined ppFEV1 increased variability as any relative increase or decrease of at least 10% in ppFEV1 from a two-year averaged baseline. A marginal structural Cox proportional hazards model was used. We examined a cumulative measure of ppFEV1 variability, defined as the cumulative proportion of visits with ppFEV1 variability at each visit. Kaplan-Meier survival curves were generated based upon quartiles of the cumulative distribution of ppFEV1 variability. MEASUREMENTS AND MAIN RESULTS: We included 9,706 CF patients in our cohort. Median age at cohort entry was 8.3 (IQR 8.2 - 8.4) years, 50% of patients were female, 94% white, and median baseline ppFEV1 was 94.4 (IQR 81.6 - 106.1). The unadjusted HR for increased ppFEV1 variability on lung transplant/mortality was 4.13 (95% CI 3.48 - 4.90) and the weighted HR was 1.49 (95% CI 1.19 - 1.86). Survival curves stratified by quartile of cumulative variability demonstrated an increased hazard of lung transplant/mortality as the proportion of cumulative ppFEV1 variability increased. CONCLUSIONS: We found a strong association between ppFEV1 variability and lung transplant or mortality in a cohort of people with CF in the US.