Independent predictors of time from symptom onset to discharge among patients with severe fever with thrombocytopenia syndrome: a retrospective cohort study

Background Severe fever with thrombocytopenia syndrome (SFTS) is a tick-borne bunyaviral infection with heterogeneous recovery trajectories and high case fatality. Most prior studies use in-hospital mortality as the primary endpoint; few quantify independent predictors of recovery duration among surviving patients. This study aimed to identify clinical and laboratory factors independently associated with total time from symptom onset to hospital discharge to guide risk stratification and targeted intervention. Methods We performed a retrospective cohort analysis of 43 consecutive laboratory-confirmed SFTS survivors discharged from Taizhou Hospital of Zhejiang Province (July 2019–April 2025). Demographics, laboratory values, and organ involvement data were extracted from electronic medical records. The primary outcome was total days from initial symptom onset to meeting standardized discharge criteria. Univariate correlation and group comparisons screened candidate variables; backward stepwise multiple linear regression was applied to identify independent predictors after multicollinearity diagnosis via variance inflation factor (VIF). Model performance was assessed using adjusted coefficient of determination (adjusted R 2 ). All statistical tests were two-sided (α=0.05). Results The mean total recovery duration was 16.58 ± 7.86 days. Univariate analysis demonstrated significant correlations between longer discharge time and three variables: prolonged platelet decline duration (r=0.6577, P<0.0001), delayed hospital admission after symptom onset (r=0.7441, P<0.0001), and presence of cardiac/circulatory involvement (P = 0.0002). Multivariate regression confirmed three independent predictors: platelet decline duration (β=0.63, P = 0.0001), cardiac/circulatory involvement (β=5.33, P = 0.0003), and days from onset to hospitalization (β=1.41, P<0.001). The final model had an adjusted R 2 of 0.7762, explaining 77.62% of variance in recovery time; all included variables had VIF<2.5 without severe multicollinearity. Conclusions Prolonged platelet decline duration, cardiovascular organ injury, and delayed hospital admission after symptom onset independently prolong hospitalization duration among discharged SFTS survivors. Dynamic monitoring of platelet counts and cardiovascular biomarkers enables risk stratification. Early hospital presentation, targeted platelet support, and cardioprotective management may shorten disease courses and optimize medical resource utilization for SFTS patients.