Pulmonary Function and Exercise-Based Assessments for the Detection of Pulmonary Hypertension in Fibrotic...

Pulmonary hypertension (PH) is a frequent complication of fibrotic interstitial lung diseases (ILDs), but its detection remains challenging due to overlapping clinical features. We aimed to evaluate the discriminatory power of physiological and exercise-based markers that differentiate right heart catheterization (RHC)-confirmed PH from low-probability ILD cases. In this prospective observational study of 59 patients with ILD, we evaluated pulmonary function tests (PFTs), cardiopulmonary exercise testing (CPET), and the 6-min walk test (6MWT). Patients deemed at high probability for clinically relevant PH following a multidisciplinary assessment were referred for RHC. Receiver operating characteristic (ROC) analysis was used to compare RHC-confirmed PH cases (n = 18) with a clinically low-probability ILD cohort (n = 19). Patients with RHC-confirmed PH had significantly lower diffusing capacity for carbon monoxide (DLCO) (43.44 ± 13.73% vs. 59.11 ± 13.50%, p = 0.002) and higher ventilatory inefficiency, as measured by the VE/VCO₂ slope (47.00 ± 7.90 vs. 40.71 ± 8.48, p = 0.035). DLCO showed moderate discriminatory performance (AUC 0.799; optimal cut-off 50.5% predicted; sensitivity 72%; specificity 72%), whereas VE/VCO₂ slope showed fair discrimination (AUC 0.711; cut-off ≈ 41.5; sensitivity 75%; specificity 59%). Although 6MWT distance did not differentiate the groups, post-exercise oxygen desaturation and heart rate were significant indicators. In fibrotic ILD, gas exchange and ventilatory inefficiency parameters-specifically DLCO and VE/VCO₂ slope-effectively discriminate RHC-confirmed PH from clinically low-probability cases. These markers offer a practical screening approach to identify patients who should be prioritized for further PH testing.