Significance of pulmonary arterial pressure and diffusion capacity of the lung as prognosticator in patients with idiopathic pulmonary fibrosis

Study objectives: To evaluate the long-term clinical course of patients with idiopathic pulmonary fibrosis (IPF) complicated with pulmonary arterial hypertension. Design: Prospective analysis of consecutive IPF patients undergoing initial workup with right-heart catheterization (RHC) and pulmonary function testing (PFT). Pulmonary arterial pressure (PAP) and diffusion capacity of the lung for carbon monoxide (DLCO) were focused on. Setting: University hospital. Patients: Seventy-eight patients with IPF (67 men, 11 women; diagnosis by pathology, n = 59; clinical diagnosis, n = 19) had been followed up after initial workup for a maximum of 14 years. Measurements and results: RHC data on 61 patients and PFT data on 52 patients were available. Five-year survival rates were 62.2% in the normal-PAP group (mean PAP < 17 min Hg, n = 37) and 16.7% in the high-PAP group (mean PAP > 17 mm Hg, n = 24) [p < 0.001]; 70.4% in the preserved-DLCO group (percentage of predicted > 40%, n = 27) and 20.0% in the low-DLCO group (percentage of predicted < 40%, n = 25) [p < 0.001];, and 82.6% in group 1 (normal PAP and preserved DLCO, n = 23) and 15.6% in group 2 (high PAP, low DLCO, or both, n = 32) [p < 0.0001]. The relative risks of mortality within 5 years after RHC were 2.20 (95% confidence interval [CI], 1.40 to 3.45) in the high-PAP group, 2.70 (95% CI, 1.46 to 4.99) in the low-DLCO group, and 4.85 (95% CI, 1.97 to 11.97) in group 2. Conclusion: DLCO was a critical factor for evaluating disease status and prognosis, and PAP status provided feasible information in the initial workup of IPF patients.