Aspartate aminotransferase-to-lymphocyte ratio predicts in-hospital mortality in patients with severe fever with thrombocytopenia syndrome: a multicenter retrospective cohort study.

backgroundSevere fever with thrombocytopenia syndrome (SFTS) is a rapidly progressive tick-borne viral disease with substantial mortality. Yet early risk stratification still lacks a simple and practical biomarker. We assessed the prognostic value of the aspartate aminotransferase-to-lymphocyte ratio index (ALRI) for in-hospital mortality in SFTS and examined whether early dynamic reassessment could further refine risk stratification.

methodsWe conducted a multicenter retrospective study of consecutive hospitalized patients with laboratory-confirmed SFTS at Yantai Qishan Hospital and Beijing Ditan Hospital between June 2022 and June 2025. Baseline ALRI was calculated as aspartate aminotransferase divided by lymphocyte count. Its prognostic performance was compared with conventional laboratory markers and viral load using receiver operating characteristic analysis, Kaplan-Meier survival analysis, Cox regression, phenotype stratification, and correlation analyses. Dynamic ALRI changes from admission to Day 7 were also assessed, and a Day 0-Day 3 two-step rule was evaluated in a Day 3 landmark cohort.

resultsAmong 220 patients, 51 died and 169 survived during hospitalization. Baseline ALRI was significantly higher in non-survivors and showed moderate discriminatory performance among the evaluated biomarkers for in-hospital mortality, with an area under the curve of 0.79 (95% confidence interval 0.72–0.85). At the optimal cutoff of 590.63, sensitivity was 78.43% and specificity was 73.37%. High baseline ALRI was associated with markedly worse survival (hazard ratio 6.91, 95% confidence interval 3.54–13.47; P < 0.001). In multivariable analyses, ALRI remained independently associated with mortality, including after adjustment for viral load. Higher ALRI was also linked to a more severe clinical profile, including greater intensive care use, higher viral load and organ injury markers, and lower lymphocyte and platelet counts. ALRI remained consistently higher in non-survivors during follow-up. Dynamic ALRI changes from admission to Day 7 were assessed when available, and the Day 0–Day 3 two-step rule was evaluated in a Day 3 landmark cohort of 214 patients. In the Day 3 landmark cohort, persistently high ALRI from Day 0 to Day 3 identified patients at particularly high risk of death.

conclusionsALRI may be useful for early risk stratification in hospitalized patients with SFTS. In addition to admission assessment, reassessment around Day 3 may help identify a persistently high-risk subgroup, particularly those with sustained ALRI elevation from Day 0 to Day 3. Prospective external validation is still needed before routine clinical application.