Prognostic Significance of Red Cell Distribution Width in Idiopathic Pulmonary Fibrosis and Combined Pulmonary Fibrosis Emphysema

Abstract

Objective: The red cell distribution width (RDW) is an inexpensive, readily available prognostic indicator of several diseases. RDW has been assessed as a prognostic biomarker in patients with idiopathic pulmonary fibrosis (IPF) in only one study; furthermore, the relationship between the RDW and combined pulmonary fibrosis emphysema (CPFE) has yet to be reported. Subjects and Methods: This single-center study was conducted between January 2015 and December 2018 in the Atatürk Chest Diseases and Chest Surgery Education and Research Hospital. Baseline characteristics, laboratory results, and survival status of patients were recorded. Results: The RDW value was significantly higher in the CPFE group than in the IPF group (median [IQR 25–75]; 16.8 [15.5–19] vs. 15.3 [13.7–16.8], p = 0.028). High RDW values were correlated with carbon monoxide diffusion capacity (DLCO) (r: −0.653 p = 0.001), 6-minute walking test (6MWT) distance (r: −0.361 p = 0.017), arterial partial oxygen pressure (PaO₂) (r: −0.692 p < 0.001), and systolic pulmonary arterial pressure (SPAP) (r: 0.349 p = 0.022) in patients with fibrotic lung disease. The RDW value was significantly higher in the exitus group than in the survivors (median [IQR 25–75]; 18.4 [15.4–19] vs. 15.2 [13.5–17.2], p = 0.016). A univariate Cox regression analysis identified DLCO, SPAP, PaO₂, and RDW as potential covariates of mortality. In a multivariate analysis, the DLCO (HR 1.21, 95% CI 1.11–1.47, p = 0.012) and RDW level (HR 1.65, 95% CI 1.09–2.47, p = 0.023) remained independent predictors of mortality. Conclusion: High RDW values appear to be a simple prognostic factor in patients with IPF or CPFE.