The Red Cell Distribution Width to Albumin Ratio as a Novel Prognostic Predictor in Patients with Severe Fever with Thrombocytopenia Syndrome: A Multicenter Study in China

Purpose: Severe Fever with Thrombocytopenia Syndrome (SFTS) is an emerging infectious disease characterized by high mortality rate. This study aimed to explore the predictive ability of the red blood cell distribution width to albumin ratio (RAR) for mortality risk in SFTS. Patients and Methods: A total of 650 hospitalized SFTS patients from two centers were randomly assigned to a training (N = 455) and validation (N = 195) cohort at a 7:3 ratio. Independent risk factors were identified by constructing the LASSO regression model and Cox regression model. The predictive power and clinical benefit of risk factors were assessed using receiver operating characteristic (ROC) and decision curve analysis (DCA), respectively, with the nomogram visualizing the model. Kaplan–Meier curve and the Log rank test were employed to compare survival probabilities. Results: The 650 patients had a median age of 66 years. Deceased exhibited a significantly higher RAR value than survivors (4.61 vs 3.77, P < 0.001). The RAR, neurological manifestations, and viral load were identified as independent risk factors for death in SFTS patients by multivariate Cox regression analysis, and the model was subsequently visualized using a nomogram. RAR demonstrated the strongest predictive performance (AUC: 0.845, P < 0.001), outperforming neurological manifestations (AUC: 0.636, P < 0.001) and viral load (AUC: 0.805, P < 0.001). In the validation cohort, RAR achieved an AUC of 0.824. Kaplan–Meier survival analysis demonstrated that SFTS patients who have RAR > 4.19 (Log rank test; χ 2 = 67.43, P < 0.001) experienced significantly lower survival rates. DCA demonstrated that the RAR had clinical net benefit for predicting mortality in SFTS patients. Conclusion: Baseline higher RAR levels were associated with an increased risk of death in SFTS patients. RAR may serve as a valuable predictor of mortality in SFTS patients during the early stage of disease.