The predictive effect of the platelet-to-lymphocyte ratio (PLR) and the neutrophil-to-lymphocyte ratio (NLR) on the risk of death in patients with severe fever with thrombocytopenia syndrome (SFTS): a multi-center study in China

BACKGROUND: Severe fever with thrombocytopenia syndrome is caused by infection with the severe fever with thrombocytopenia syndrome virus. METHODS: Between April 2011 and December 2019, data on consecutive patients who were diagnosed with severe fever with thrombocytopenia syndrome were prospectively collected from five medical centers in China. The score of the death risk model was correlated with the platelet-to-lymphocyte ratio and the neutrophil-to-lymphocyte ratio. Multivariable Cox analyses were used to identify the independent factors associated with mortality. RESULTS: During the study period, 763 patients were diagnosed with severe fever with thrombocytopenia syndrome; 415 of these patients were enrolled in our study. We found that the neutrophil-to-lymphocyte ratio of the group that died was significantly higher on admission (P=0.007) than that of the group that survived, and the neutrophil-to-lymphocyte ratio showed a positive correlation with the score of the death risk model. Multivariate Cox regression suggested that a neutrophil-to-lymphocyte ratio greater than 5.4 was an independent risk factor for survival time (HR=6.767, P=0.011). Platelet-to-lymphocyte ratio did not show a special role in this study. CONCLUSIONS: A neutrophil-to-lymphocyte ratio greater than 5.4 can increase the risk of death and decrease the survival time of patients. In summary, the neutrophil-to-lymphocyte ratio provides a supplementary means for effectively managing severe fever with thrombocytopenia syndrome (SFTS).