[The importance of lung function as a predictor of 2-year mortality in mucoviscidosis]

Prediction of mortality in cystic fibrosis (CF) has become an important issue in the era of lung transplantation. A study from Toronto has shown a forced expiratory volume in one second (FEV1) below 30% predicted to be the best predictor of two-year mortality. The purpose of this investigation was to assess whether these data are relevant for other CF centers with a different overall life expectancy. We have analysed pulmonary function tests (PFTs) obtained in our population of CF patients between 1979 and 1991. 19 of the 73 patients included in this analysis had died. Cox proportional hazard regression analysis was performed using the lung function parameters as single covariates. In addition results of PFTs obtained two years before death were compared to similarly lagged values of surviving patients. Inspiratory vital capacity (IVC) (p < 0.0001), the ratio of residual volume/total lung capacity (RV/TLC) (p < 0.0001), forced expiratory volume in one second (FEV1) (p < 0.0002), specific conductance (sGaw) (p < 0.025) and a weight for height below the third percentile (p < 0.023) were significant predictors of two-year mortality. Two-year mortality were 50% for a FEV1 < 30% predicted and 47% for a RV/TLC ratio > 50%. Our data confirm that a FEV1 < 30% and a RV/TLC ratio > 50% are significant predictors of mortality in CF. However, interindividual variability in survival with a FEV1 < 30% is high. The decision for lung transplantation can therefore not be based on pulmonary function alone.