NLPR as a predictor of poor prognosis in patients with severe fever with thrombocytopenia syndrome: a prospective longitudinal study.

BACKGROUND AND AIMS: Severe fever with thrombocytopenia syndrome (SFTS) is an emerging tick-borne infectious disease characterized by high mortality and rapid clinical progression. This longitudinal study aimed to investigate the temporal changes in laboratory parameters and evaluate the prognostic value of hematology-derived systemic inflammatory indices in patients with SFTS.

METHODS

Altogether, 235 hospitalized patients with SFTS were prospectively enrolled between 2022 and 2024. Demographic, clinical, treatment, and outcome data were collected and reassessed. Hematological, liver, and kidney function parameters, and myocardial parameters were routinely measured on days 0, 3, 7, and 10 after admission. Time-points stepwise Cox proportional hazards regression and receiver operating characteristic (ROC) curve analyses were performed at each time point to evaluate predictive performance.

RESULTS

Of the 235 patients, 61 (26.0%) died of SFTS. The median age was 64.0 (IQR 54.0-71.0) years, and 93 (39.6%) were male. After adjusting for confounding factors, serum creatinine (HR 1.017 [95% CI 1.006-1.029], p = 0.003), urea (HR 1.102 [95% CI 1.047-1.161], p < 0.001), platelet counts (HR 0.987 [95% CI 0.977-0.997], p = 0.010), neutrophil-to-lymphocyte-platelet ratio (NLPR) (HR 1.021 [95% CI 1.007-1.034], p = 0.002), and neutrophil percentage-to-albumin ratio (NPAR) (HR 1.689 [95% CI 1.028-2.776], p = 0.039) were identified as independently associated with prognosis at each time point. Among them, NLPR presented consistently high predictive performance, with an area under the curve (AUC) of 0.802 (95% CI 0.736-0.868) on day 0, 0.833 (95% CI 0.774-0.892) on day 3, 0.861 (95% CI 0.784-0.938) on day 7, and 0.840 (95% CI 0.706-0.975) on day 10. Patients with high NLPR (> 3.76) had significantly shorter survival times (HR 6.584 [95% CI 3.840-11.290], p < 0.001 by the log-rank test). In addition, albumin treatment was associated with a reduced risk of mortality in the high-NLPR group (HR 0.423 [95% CI 0.195-0.919], p = 0.030).

CONCLUSIONS

NLPR may serve as a simple and effective prognostic marker for SFTS. Albumin treatment may be associated with a lower risk of mortality in patients with a high NLPR.