Background: The pulmonary diffusing capacity for carbon monoxide corrected for hemoglobin (DLCOc) is reduced in individuals with pulmonary hypertension (PH) due to different pathomechanisms depending on the cause of PH. However, the clinical significance remains unclear. We sought to investigate the impact of DLCOc on long-term survival in patients with PH.

Methods: We conducted a retrospective cohort study of 341 patients with PH referred to a tertiary hospital for evaluation between January 2011 and January 2020. Patients were included from all five PH groups: Group 1 (Pulmonary arterial hypertension, n=152), Group 2 (PH related to left heart disease, n=27), Group 3 (PH related to lung disease or hypoxia, n=30), Group 4 (PH associated with pulmonary artery obstructions, n=122), and Group 5 (PH of unclear or multifactorial etiology, n=10).

Results: Following multivariable analysis adjusted for univariate negative predictors of survival, only predicted DLCOc and hemoglobin were identified as a negative survival risk factor. This relationship remained in the adjusted analysis (DLCOc: HR 0.9643, 95% CI: 0.9488 to 0.9801, p < 0.001. Hemoglobin: HR 0.8245, 95% CI: 0.6962 to 0.9766, p = 0.025) across PH subgroups.

Conclusion: Reduced predicted DLCOc and hemoglobin are independent predictors of death in PH patients regardless of PH subgroup, supporting the clinical use of these metrics for prognostic stratification and disease progression.