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. The 165 patients with baseline hemoglobin, RDW and date of diagnosis available constituted the analytical cohort. An HRR cutoff (≤ 0.86) was derived by time-dependent ROC 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, PAPs 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.