GAP scoring system in IPF patients treated with antifibrotics: prognostic performance and 1- to 3- years mortality: a retrospective study

Introduction: To inform IPF patients about the expected prognosis of their disease, the GAP stage system was developed, a scoring system encompassing age, gender, FVC% and DLCO%. However, survival rates were determined in an untreated IPF cohort. Aims: The objective of this study was to evaluate the GAP stage system as a prognostic tool and provide GAP-stratified survival data, in an IPF cohort treated with antifibrotics. Methods: We included all MDT-discussed IPF patients treated with antifibrotics in UZ Leuven. The association of age, gender, FVC%, DLCO%, GAP stage and GAP score with survival was assessed using cox proportional hazards models. Moreover, 1- to 3-year mortality was calculated for every GAP stage. Results: 537 treated IPF patients were included in the study. Mean age at diagnosis was 71.4 ± 8.3, 78% was male. FVC% was 84.9% ± 17.7%, DLCO% 50.4 % ± 14.5%. Mean follow-up time was 2.5 years. Age, gender, FVC% and DLCO% were all associated with death, both in univariate and multivariate analysis. GAP score was associated with death (HR 1.76, p<0.001) as well as GAP stage (HR 2.5, p<0.001, Figure 1a). 1- to 3-year mortality rates stratified by GAP stage are shown in Figure 1b. Conclusion: The GAP stage system is a reliable instrument to predict prognosis, also in treated IPF patients, being strongly associated with 1- to 3-year survival.