The FEV1/DLCO Ratio as an Effective Predictor of Severity and Survival in COPD-Associated Pulmonary Hypertension

Background: Pulmonary hypertension (PH) frequently complicates chronic obstructive pulmonary disease (COPD), significantly increasing morbidity and mortality. Although right-heart catheterization (RHC) is the diagnostic gold standard, non-invasive markers for estimating PH severity remain crucial. Recent studies suggest that the forced vital capacity (FVC)/diffusing capacity (DLCO) ratio predicts PH, but the utility of FEV1/DLCO remains underexplored. Objective: To determine whether the FEV1/DLCO ratio predicts PH severity in COPD-PH and to compare its diagnostic performance with the FVC/DLCO ratio. Methods: A cross-sectional study was conducted over six months among COPD outpatients. After screening for inclusion and exclusion criteria, pulmonary function testing and transthoracic echocardiography were performed. FEV1/DLCO and FVC/DLCO ratios were correlated with mean pulmonary arterial pressure (mPAP). Results: FEV1/DLCO strongly correlated with PH severity (r = 0.78; p < 0.001) and demonstrated a higher predictive accuracy for severe PH (AUC = 0.88) compared to FVC/DLCO (AUC = 0.72). An FEV1/DLCO cutoff of >2.5 predicted severe PH with 86% sensitivity and 81% specificity. Conclusion: The FEV1/DLCO ratio is a superior non-invasive marker for predicting PH severity in COPD-PH compared with FVC/DLCO. This ratio may improve risk stratification and guide timely referral for invasive evaluation and management.