Introduction: The Gender-Age-Physiology (GAP) system is a tool for predicting prognosis in patients with idiopathic pulmonary fibrosis (IPF). Yet, to date, the GAP system has not been evaluated in patients with IPF who received nintedanib.
Material and methods: This single-center retrospective study included 89 patients with IPF who received Nintedanib for at least 3 months. All-cause mortality was set as the end point. Clinical parameters, including the GAP stage, were statistically analyzed for risk factors leading to mortality using the Cox proportional hazard model.
Results: The median follow-up was 16.4 months (range 3.7-37.4 months), during which 23 patients died. Univariate analysis revealed that the GAP stage (hazard ratio [HR] 3.00, 95% confidence interval [CI] 1.52-5.92, p = 0.0014) and PaO2 (HR 0.95, 95% CI 0.92-0.98, p = 0.0063) were significant prognostic factors. Multivariate analysis revealed that the GAP stage was a significant prognostic factor (HR 2.26, 95% CI 1.07-4.78, p = 0.031). Log-rank analysis revealed that there were no significant differences in "Gender" (p = 0.47) and "Age" (p = 0.18) factors. However, there were significant differences in "Physiology" factors (% of forced vital capacity, p = 0.018; % of diffusing capacity of lung carbon monoxide, p < 0.001). The cumulative incidences of mortality at 1 and 2 years were as follows: GAP I: 5.1% and 6.8%; GAP II: 9.5% and 29.3%; and GAP III: 18.9% and 84.2%.
Conclusions: The GAP system is useful as a prognostic tool in patients with IPF who have been treated with nintedanib.
Keywords: GAP stage; diffusing capacity of lung carbon monoxide; forced vital capacity; idiopathic pulmonary fibrosis; nintedanib.