Abstract: Objective　To investigate the effect of the systemic immune-inflammation index (SII) on the conversion time of virus nucleic acid turning negative in patients with coronavirus disease 2019 (COVID-19). Methods　A total of 127 patients were selected who were admitted to our hospital from January to March 2020. Clinical data and laboratory results within 24 hours of admission were obtained from the electronic medical record system. Blood routine results were recorded to calculate SII. According to the median SII, the patients were divided into the high SII group (≥393) and the low SII group (<393). The clinical data, neutrophil-lymphocyte ratio (NLR), platelet-lymphocyte ratio (PLR), C-reactive protein (CRP), interleukin(IL)-6 and albumin (ALB) were compared between the two groups. Cox regression analysis was performed to identify risk factors affecting the negative time of viral nucleic acid. Kaplan-Meier analysis was used to describe the nucleic acid turning negative curve of different groups of patients. Results　The male proportion, NLR, PLR and CRP were higher in the high SII group than those in the low SII group (P＜0.05). Cox multivariate regression analysis showed that severe patients, higher SII and the time from onset to admission > 5 days were independent risk factors affecting the time of nucleic acid negative conversion (P＜0.05). Kaplan-Meier curve showed that the median nucleic acid turning negative time was significantly longer in patients with high SII value, severe disease and time from onset to admission > 5 days than that in patients with low SII value, non-severe disease and time from the onset to admission ≤5 days (P＜0.05). Conclusion　SII is a simple biomarker representing inflammation and the immune response. It can be used as an independent risk factor for prolonged nucleic acid negative conversion time in COVID-19 patients.

Key words: pneumonia, viral, coronavirus, COVID-19, SARS-CoV-2, systemic immune-inflammation index, time of nucleic acid turning negative