Hemoglobin-to-RDW Ratio and All-Cause Mortality in Idiopathic Pulmonary Fibrosis: Complementary Value to Echocardiographic Right Ventricular–Pulmonary Arterial Coupling

Background: The hemoglobin-to-red cell distribution width ratio (HRR) is a composite hematologic biomarker that integrates oxygen-carrying capacity and inflammation-related erythrocyte variability. Its prognostic value in idiopathic pulmonary fibrosis (IPF), and its relationship with right ventricular (RV) function, have not been established. Methods: We conducted a single-center retrospective study of 198 patients with IPF. A total of 165 patients with baseline hemoglobin, red cell distribution width (RDW) and date of diagnosis available constituted the analytical cohort. An HRR cutoff (≤0.86) was derived by time-dependent Receiver Operating Characteristic (ROC) curve analysis at 5 years. All-cause mortality from diagnosis was assessed by Kaplan–Meier and Cox regression, with bootstrap internal validation. Associations between hematologic markers and TAPSE (Tricuspid Annular Plane Systolic Excursion), PAPs (pulmonary arterial systolic pressure) and TAPSE/PASP were examined by linear and logistic regression, followed by joint stratification of HRR and RV–PA coupling. Results: Over a median follow-up of 70.3 months, 57 patients (34.5%) died. Low HRR was associated with higher mortality (72.7% vs. 15.5%; adjusted HR 3.07, 95% CI 1.68–5.63; optimism-corrected HR 2.37) and improved a clinical model beyond RDW (likelihood-ratio p = 0.012). HRR was not associated with TAPSE, PAPs, TAPSE/PASP or RV–PA uncoupling. In exploratory joint stratification, mortality rose from 11.7% with both markers preserved to 100% with both abnormal (age-adjusted HR 6.47, 95% CI 2.64–15.86). At 5 years, HRR and RDW showed similar discrimination (time-dependent AUC 0.70 and 0.71), higher than TAPSE/PASP (0.61). Conclusions: HRR is a simple, inexpensive and independent predictor of mortality in IPF that is unrelated to RV–PA coupling. The two markers provide complementary prognostic information, and their combination identifies a subgroup at very high risk. These findings require external validation.