Difference in hematocrit and plasma albumin levels as an early biomarker of severity and prognosis in patients with severe fever and thrombocytopenia syndrome

Severe fever with thrombocytopenia syndrome (SFTS) is a widespread infectious disease with high mortality. Hence, identifying valuable biomarkers for detecting the early changes in SFTS is crucial. In this study, we investigated the relationship between the difference in hematocrit (HCT) and serum albumin (ALB) levels (HCT-ALB) and the prognosis of patients with SFTS virus infection. After excluding the patients who did not meet the SFTS diagnostic criteria, those with SFTS from the First Affiliated Hospital of Wannan Medical College were divided into a fatal and Nonfatal group based on their disease prognosis. A dynamic analysis of the daily laboratory data was conducted for 14 days following SFTS onset. A receiver operating characteristic (ROC) curve was used to evaluate the predictive value of HCT-ALB. Another sample of patients with SFTS admitted to the First Affiliated Hospital of Nanjing Medical University was utilized to verify the study conclusions. A total of 158 patients with SFTS were included. Among them, 126 patients were categorized in the Nonfatal group and 32 in the fatal group, leading to a mortality rate of 20.25% (32/158). Univariate analysis of the laboratory test findings and ROC curve analysis showed that alanine aminotransferase (ALT), aspartate aminotransferase (AST), HCT-ALB, and lactate dehydrogenase (LDH) had a relatively better ability to discriminate the disease condition of the patients with SFTS. Moreover, HCT-ALB served as a predictor of SFTS prognosis. Additionally, an area under the ROC curve (AUC) of 0.777 and a critical HCT-ALB value of 4.75 on day 7 were associated with a sensitivity of 83.3% and a specificity of 73.9%. On day 8 (AUC = 0.882), the critical value of HCT-ALB was 9.25, while the sensitivity was 100% and specificity was 76.5%. Further verification based on the data of 91 patients with SFTS admitted to the First Affiliated Hospital of Nanjing Medical University demonstrated a mortality rate of 51% (24/47) among those with HCT-ALB values >4.75 on day 7 of the disease course, highlighting the potential of the HCT-ALB value of >4.75 for predicting SFTS prognosis. High HCT-ALB values are closely related to the mortality of patients with SFTS. HCT-ALB is a sensitive and independent predictor of early disease in patients with SFTS.