Precise staging of severe fever with thrombocytopenia syndrome: Integrating the extent of organ damage for prognostic and therapeutic applications.

OBJECTIVES: This study aimed to develop an accurate staging system for SFTS (Severe Fever with Thrombocytopenia Syndrome) based on the dynamic assessment of organ damage. This staging is intended to improve prognostication and guide treatment strategies. METHODS: Clinical data and laboratory parameters were analyzed from 77 fatal and 398 non-fatal cases of SFTS. Risk factors for mortality were identified using univariate Cox regression analysis. Dynamic changes in laboratory parameters and multi-organ dysfunction were systematically observed. RESULTS: By dynamically analyzing clinical symptoms and laboratory parameters over the disease course, combined with assessing the number and severity of multi-organ dysfunction, SFTS progression was categorized into five distinct stages: initial (1-4 days), progressive (5-7 days), MOD (Multiple Organ Dysfunction) (8-10 days), remission (11-14 days), and convalescence (15-20 days). The critical phase, lasting approximately two weeks, accounted for 85.71% of patients succumbed within this two-week period, with 46.75% experiencing mortality during the MOD stage. Moreover, the study findings highlighted the effectiveness of intravenous immunoglobulin, including both its overall and early administration, in improving outcomes for patients with SFTS-associated myocarditis. CONCLUSIONS: The progression of SFTS can be distinctly categorized into five distinct stages. Day 7 represents a critical juncture in disease progression, whereas Day 11 signifies a pivotal moment for clinical recovery. The progression stage is optimal for intervening to prevent further disease advancement. Treatment strategies should be adapted to the evolving patterns and severity of organ dysfunction. Myocarditis remains a significant challenge throughout SFTS progression, and early IVIG administration has been demonstrated to reduce mortality in patients with myocarditis complications significantly.