Clinical outcomes and safety of tocilizumab in severe fever with thrombocytopenia syndrome: a retrospective multicenter cohort study.

BACKGROUND: Severe fever with thrombocytopenia syndrome (SFTS) is an emerging tick - borne zoonotic infectious disease. Severe SFTS cases exhibit an extremely high fatality rate, but there remain no effective clinical treatments. METHODS: Propensity Score Matching (PSM) and logistic regression analysis were used to assess the efficacy, safety, and baseline factors influencing patient prognosis of tocilizumab in the treatment of SFTS. RESULTS: A total of 833 SFTS cases were included, of whom 171 received tocilizumab. After PSM, a higher recovery rate was observed in the tocilizumab group than in the control group (76.61% vs 67.70%, P = 0.039). However, the between-group difference in in-hospital mortality did not reach statistical significance after matching (16.96% vs 15.22%, P = 0.322). Regarding selected adverse events (AEs) such as co-infection, the between-group differences did not reach statistical significance; these represent observed differences in retrospectively recorded data and should not be interpreted as evidence of safety. Multivariable logistic regression showed that age ≥ 65 years, vasopressor therapy, platelet transfusion, and Ct value were associated with prognosis among tocilizumab-treated patients, with vasopressor use and platelet transfusion likely reflecting disease severity rather than independent causal determinants. CONCLUSION: In this retrospective cohort, after PSM, tocilizumab use was associated with a higher recovery rate in SFTS patients, although the between-group difference in in-hospital mortality did not reach statistical significance. Observed differences in selected AEs were based on retrospectively recorded data and should not be interpreted as evidence of safety. Given the exploratory nature, prospective studies are warranted.