Pulmonary hypertension in idiopathic pulmonary fibrosis does not influence six-minute walk distance: results from a retrospective study

Background: The characteristics of the six-minute walk test (6MWT) in patients with idiopathic pulmonary fibrosis (IPF) and pulmonary hypertension (PH) have not yet been described; nevertheless, this test has already been used as a "surrogate end point" in some clinical trials.Objective: Goal of this retrospective study was to assess whether the presence of PH in patients with IPF might influence 6MWT performances.Methods: We retrospectively reviewed the data of patients with IPF who were referred to our hospital. The study population was divided in two groups according to the presence or absence of PH at right heart catheterization; then, the six-minute walking distance (6MWD) and pulmonary function tests (PFTs) were compared between groups.Results: Study population included 30 IPF patients with a mean age of 59.0 years (± 8.3), most of whom (76.7%) were males. A total of 43.3% of patients had PH.PFTs data were similar in IPF patients of the two groups; the only exception was FVC, which was significantly higher in IPF patients with PH (63.8% ± 16.0 vs. 51.6% ± 13.8 in patients without PH, p<0.05). No difference was detected between groups in 6MWD (222.3m ± 118.5 in PH group and 222.1m  ± 118.5 in non-PH group, p>0.05).Conclusions: Our data suggested that 6MWD does not differ between IPF patients with or without PH. Thus, 6MWD should not be used as a surrogate endpoint in clinical study in patients affected by IPF and PH.