Cardiopulmonary Exercise Testing Provides Prognostic Information in Advanced Cystic Fibrosis Lung Disease

Rationale: Cardiopulmonary exercise testing (CPET) provides prognostic information in cystic fibrosis (CF); however, its prognostic value for patients with advanced CF lung disease is unknown. Objectives: To determine the prognostic value of CPET on the risk of death or lung transplant (LTX) within 2 years. Methods: We retrospectively collected data from 20 CF centers in Asia, Australia, Europe, and North America on patients with a forced expiratory volume in 1 second (FEV₁) < 40% predicted who performed a cycle ergometer CPET between January 2008 and December 2017. Time to death/LTX was analyzed using mixed Cox proportional hazards regression. Conditional inference trees were modeled to identify subgroups with increased risk of death/LTX. Results: In total, 174 patients (FEV₁, 30.9% 6 5.8% predicted) were included. Forty-four patients (25.5%) died or underwent LTX. Cox regression analysis adjusted for age, sex, and FEV₁ revealed percentage predicted peak oxygen uptake (V^_ O_2peak) and peak work rate (W_peak) as significant predictors of death/LTX: adjusted hazard ratios per each additional 10% predicted were 0.60 (95% confidence interval, 0.43-0.90; P = 0.008) and 0.60 (0.48-0.82; P, 0.001). Tree-structured regression models, including a set of 11 prognostic factors for survival, identified W_peak to be most strongly associated with 2-year risk of death/LTX. Probability of death/LTX was 45.2% for those with a W_peak < 49.2% predicted versus 10.9% for those with a W_peak. 49.2% predicted (P, 0.001). Conclusions: CPET provides prognostic information in advanced CF lung disease, and W_peak appears to be a promising marker for LTX referral and candidate selection.