Pulmonary diffusion capacity to select patients for echocardiographic evaluation of pulmonary hypertension in interstitial lung disease: Impact of interstitial lung disease phenotype

Background Treprostinil inhalation for pulmonary hypertension (PH) with interstitial lung disease (ILD) has increased the importance of PH screening. We aimed to determine whether pulmonary function tests performed for ILD management could identify patients with possible PH on echocardiography, according to ILD subtype. Methods In this cross-sectional study, patients with ILD who underwent pulmonary function tests and echocardiography within three months were enrolled consecutively. The correlation between pulmonary function test results and peak tricuspid regurgitation velocity (TRV) was assessed using Spearman's rank correlation coefficient. We defined possible PH as peak TRV > 2.8 m/s. The screening performance for possible PH was evaluated using ROC analysis. Results In total, 278 patients were analysed. Among pulmonary function test values, percent predicted diffusing capacity of the lung for carbon monoxide (%DLCO) most significantly correlated with TRV (ρ = −0.468, p < 0.001). In the ROC curve analysis for identifying possible PH, %DLCO exhibited the highest area under the curve (AUC) of 0.750. The AUC for combined pulmonary fibrosis and emphysema (CPFE), idiopathic interstitial pneumonias (IIPs), and collagen vascular disease-related interstitial pneumonia (CVD-IP) were 0.856, 0.747, and 0.671, respectively. Among patients with IIPs, the AUC was higher when Brinkman Index was ≥600 than when it was <600 (0.881 vs 0.620). Conclusions Based on numerical trends, %DLCO showed potentially high screening performance in patients with CPFE or IIPs with a history of heavy smoking. Echocardiographic evaluation for possible PH may be warranted in this population with reduced %DLCO.