Association of Red Blood Cell Distribution Width Levels with Connective Tissue Disease-Associated Interstitial Lung Disease (CTD-ILD)

Abstract

Objective. The aim of this study was to evaluate the diagnostic and prognostic value of red blood cell distribution width (RDW) in patients with connective tissue disease-associated interstitial lung disease (CTD-ILD). Methods. We retrospectively reviewed 213 CTD-ILD patients and 97 CTD patients without ILD from February 2017 to February 2020. Hospital and office records were used as data sources. CTD-ILD patients were followed up. Results. Patients with CTD-ILD had significantly higher RDW than those with CTD without ILD ( $p<0.001$ ). The area under the receiver operating characteristic curve (AUROC) of RDW for discriminating CTD-ILD from CTD without ILD was 0.64 (95% CI: 0.57-0.70, $p<0.001$ ). The cutoff value of RDW for discriminating CTD-ILD from CTD without ILD was 13.95% with their corresponding specificity (55.9%) and sensitivity (70.1%). Correlation analyses showed that the increased RDW was significantly correlated with decreased DLCO%predicted ( $r=-0.211$ , $p=0.002$ ). Cox multiple regression analysis indicated that RDW ( $\text{HR}=1.495$ , $p<0.001$ ) was an independent factor in the survival of CTD-ILD. The best cutoff value of RDW to predict the survival of patients with CTD-ILD was 14.05% ( $\text{AUC}=0.78$ , 95% CI: 0.72-0.84, $p<0.001$ ). The log-rank test showed a significant difference in survival between the two groups ( $\text{RDW}>14.05\%$ and $\text{RDW}<14.05\%$ ). Conclusion. RDW was higher in CTD-ILD patients and had a negative correlation with DLCO%predicted. RDW may be an important serum biomarker for severity and prognosis of patients with CTD-ILD.