In December 2019, a new infectious disease, the COVID-19, swept through Wuhan and quickly spread to all Chinese cities and dozens of countries overseas. The infectious disease is highly infectious, which could occur human-to-human transmission among close contacts and spreads over a wide area[7, 8]. However, its source is not fully clear, and the lack of specific treatment drugs which may cause the patient's symptoms to progress from mild to severe, or even death. Previous studies reported that the fatality rate among hospitalized COVID-19 patients was about 2.3%, which was much lower than those of SARS and Middle East Respiratory Syndrome (MERS) infected patients[4, 9]. For such patients, we need to strengthen vigilance, and give symptomatic support treatment early to reduce the occurrence of severe diseases.
In our retrospective cohort study, we included100 COVID-19 patients from a single clinical center in Hangzhou, Zhejiang province. Our result showed that age and BMI were independent risk factor of severe illness. The median age was 54 years. 63% of the patients were older than 50 years, which was consistent with multiple reported literature[10, 11]. Severe patients were much older than nonsevere ones and may be relate to lower immunity response and higher frequency of underlying conditions, which were not good for a self-limited recovery after virus infection. In addition, we discovered that overweight (BMI༞24) was an important risk factor of severity in COVID-19 patients. Compared with the BMI value of severe patients,nonsevere cases was lower. And there was significant differences between the two groups (P = 0.0339).
Like H7N9, the most common symptoms of COVID-19 patients were fever and cough[5, 12]. However, there were still 26% COVID-19 patients, who were admitted to our hospital with normal temperature. Once these patients were ignored, more people might be infected. It was similar to previous reports. Coexisting disorder such as hypertension and diabetes mellitus were associated with severe illnesses. The proportions of hypertension and diabetes mellitus in severe illnesses were higher than those in non-severe cases. Furthermore, hypertension was significantly different between the two groups (P < 0.0001). This was consistent with H7N9 Patients. In addition, we also found that Laboratory parameters and supplementary treatment in single variable analysis identified as risk factors for severe illnesses including the white blood cell count, d-dimer, C-reactive protein, procalcitonin, alanine aminotransferase, IL6, IL10, the total number of T cells, B cell, absolute number of lymphocytes, TH/induced T cells, TS/ Tc cells and the need for antibiotic treatment, glucocorticoid and artificial liver therapy, but these risk factors did not reach our criteria of our multivariate analysis.
Previous studies found that inflammatory factor storm was one of the important factors for severe illness and even death of H7N9, SARS-CoV, MERS- CoV. The mechanism may be related to the overexpression of inflammatory factors and chemokines, which can lead to acute lung injury and ARDS[1, 15, 16]. In our retrospective study, we also found a significant increase in cytokine IL6 in the severe patients. Therefore, for patients with the gradual increase expression of such inflammatory factors, early low-dose glucocorticoid and artificial liver treatment may alleviate the progress of the disease and reduce the risk of death. The effectiveness and necessity of glucocorticoid use has been controversial in novel coronavirus infections. Large doses of glucocorticoids may cause significant side effects such as lymphocytopenia and femoral head necrosis. In our cohort, the rates of treatments with glucocorticoid and artificial liver in the severe group were greater than those in the non-severe group, and there were statistical differences. However, there were no statistically difference in treatment effect between the two groups (the days from treatment initiation to virus clearance) (supplementary Fig. 1–2), which may be related to our small sample size. Further research on larger samples is in progress. Our study found that the number of immune cells in most patients with mild disease is normal. The decrease of T lymphocyte, B lymphocyte and absolute Lymphocyte count are positively correlated with the severity of the disease. Therefore, early detection of related immune indicators may provide us with the ability to predict the severe tendency. Furthmore, we need more samples to confirm whether these factors are the severity of the disease.
There are several limitations to be considered when interpreting the findings. First, our study is a single-center study of COVID19 risk factors for critically ill patients in a hospital. Furthermore, when screening confirmed cases, the vast majority of lower respiratory tract specimens were used, but there were still a few patients who collected pharyngeal swab specimens, and their false negative rate may lead to the lack of included patients. Finally, the number of children under 18 years in our sample was small, so no specific conclusions could be drawn for adolescents.