Red Cell Distribution Width to Red Blood Cell Ratio: A Novel Biomarker for Predicting 30-Day Mortality in Type B Acute Aortic Dissection.

Abstract

Background: Type B acute aortic dissection (BAAD) is associated with significant morbidity and mortality. Early identification of high-risk patients remains challenging. This study aimed to investigate whether the ratio of red cell distribution width to red blood cell count (RRR) could serve as a novel prognostic biomarker for 30-day mortality in patients with BAAD.

Methods: This retrospective cohort study enrolled 126 BAAD patients between 2017 and 2019. The primary outcome was 30-day mortality. To mitigate overfitting and identify robust predictors from a comprehensive panel of laboratory parameters, we employed the Boruta algorithm for feature selection, followed by variance inflation factor (VIF) analysis to assess multicollinearity. Variables with VIF > 5 were excluded. An optimal RRR cutoff was determined using receiver operating characteristic (ROC) analysis. The Boruta algorithm and multivariate logistic regression were used to identify independent predictors.

Results: During the 30-day follow-up period, 16 deaths (12.7%) were recorded. Comparative analysis showed that nonsurvivors had significantly lower RBC counts and hemoglobin, higher RDW, and markedly elevated RRR compared to survivors (all p < 0.05). The AUC for RRR was 0.774 (95% CI: 0.672-0.876) (RBC AUC = 0.741; RDW AUC = 0.684). However, the prognostic performance of RRR was not statistically superior to that of RDW alone (DeLong's test, p = 0.155) or RBC alone (DeLong's test, p = 0.335). After Boruta selection and VIF-based exclusion of collinear variables (AST and RBC, both VIF > 5), the final multivariable logistic regression model included RRR, ALT, PLT, and CREA. In multivariate analysis, only RRR remained independently associated with mortality within this model (OR = 3.059, 95% CI: 1.431-6.540, p = 0.004).

Conclusion: The RRR, a simple index derived from routine blood tests, was independently associated with 30-day mortality within our laboratory-based model in patients with BAAD. Given this association, the RRR warrants prospective validation as a prognostic tool.