Clinical symptomatology, laboratory findings and risk score for severe fever with thrombocytopenia syndrome

December 31, 2018

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Several studies have now described severe fever with thrombocytopenia syndrome (SFTS) but the description of its clinical features have still not been fully addressed by a large study. The authors therefore wanted to examine the clinical features of SFTS in a large population of patients in an endemic area. They performed a prospective observational study in which data were collected on patients admitted to a hospital in Xinyang, Henan Province, China, with laboratory-diagnosed SFTS. They collected demographic, clinical, laboratory and treatment data for each patient and followed them up within 2 weeks after discharge or discontinuation of treatment. Between 2011 and 2017, 2096 patients with laboratory-confirmed SFTS were admitted to the hospital. The mean age at admission was 61·4 years and 59% were female. The case fatality rate (CFR) was 16·2%. A higher risk of death was associated with: being male (unadjusted odds ratio [OR] 1·45, 95%CI 1·15-1·83), being older (for a 10-year increase, unadjusted OR 1·82, 95%CI 1·62-2·04), experiencing a longer delay in admission (for every extra day taken before admission to hospital, unadjusted OR 1·18, 95%CI 1·12-1·24), the presence of diarrhoea (adjusted OR 1·44, 95%CI 1·12-1·87) or dyspnoea (adjusted OR 8·35, 95%CI 5·97-11·69), and the development of haemorrhagic signs (adjusted OR 2·79, 95%CI 2·18-3·57) or neurological symptoms (adjusted OR 30·26, 95%CI 21·39-42·81). The laboratory variables that were associated with death included high levels of lactate dehydrogenase, aspartate aminotransferase and blood urea nitrogen, and an abnormal neutrophil percentage. These, together with age and neurological symptoms, were then combined to produce a clinical scoring system. The authors found that a total score of >8 was the optimal threshold to predict risk of death for patients who were evaluated within 6 days following symptom onset (area under the curve 0·879). For all patients, viraemia was a strong predictor of fatal outcome. Ribavirin therapy was found to be effective in reducing CFR from 6·25% to 1·16%, but only in patients with a viral load <10^6 copies/mL (hazard ratio 9·72, 95%CI 1·30-72·87). Therefore the changing epidemiology and high CFR of SFTS means that this disease requires continuous surveillance. An early prediction of fatal outcome can be attained by monitoring clinical and laboratory data, with ribavirin used early, particularly before the viral load reaches 10^6 copies/mL.

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Li H, Lu QB, Xing B, Zhang SF, Liu K, et al. ISSN: Lancet Infect Dis; 18(10): 1127-1137


Added: December 31, 2018