Nowadays, COVID-19 outbreak has caused widespread concern and threatened the global public health security. This retrospective cohort study included 415 COVID-19 patients, among which 29 (7%) were severe. This is different from reports from Wuhan, China[2, 10]. The clinical, laboratory, and radiographic features in this cohort of patients with COVID-19 in Shanghai were nonspecific and similar to those in other series[1–4, 11, 12]. Recently, the epidemics has transmitted from the first stage, in which imported cases composed of the main laboratory-confirmed cases in Shanghai. Compared with patients who had non-severe COVID-19, patients with severe COVID-19 had lower lymphocyte percentage, lymphocyte counts, monocyte percentage, and higher neutrophil percentage, neutrophil counts at presentation. These patients may have had a higher viral load at presentation, which may have led to the apparently worse of laboratory values. We also compared NLR and PLR, the two groups have significantly differences. This probably due to their viral load and immune state. Lactate dehydrogenase, C-reactive protein (CRP), and D-dimer, prothrombin time, FDP, BNP were higher in severe groups than in non-severe groups. From Guang Chen’s research, they found that the SARS-CoV-2 infection may affect primarily T lymphocytes particularly CD4 + T and CD8 + T cells, resulting in decrease in all numbers as well as IFN-γ production[11]. Our data analyzed these immune markers in order to find the cause of severity of COVID-19.
In this cohort, we observed that 66.0% of the patients had at least one underlying disorder (i.e., hypertension, diabetes, coronary heart disease), and a higher percentage of hypertension and fatty liver in the severe cases than the non-severe individuals, in consistent with other studies[12, 13] .The risk factors for severity included age, high LDH level, and high d-dimer level in previous reports[8]. However, different from the findings of previous studies, we found coronary heart disease and fatty liver were the comorbidity associated with the severity of COVID-19.
The NLR was higher in severe cases than in non-severe cases which is consistent with recent studies[8, 9]. Besides, we found PLR was also higher in severe patients compared with non-severe patients. Numerous observational studies have suggested that the NLR, LMR, lymphocyte proportion and the PLR are inflammatory markers of immune-mediated, metabolic, prothrombotic, and neoplastic diseases, and are widely investigated as useful predictors for prognosis in many diseases[5–7]. The results of this study have several clinical implications and strengths. Since NLR and PLR could be quickly calculated based on a blood routine test on admission, so we should pay attention to these laboratory findings to identify high risk COVID-19 patients.
Recent researches focus on asymptomatic infection[14, 15], possible fecal-oral transmission in SARS-Cov-2 infection[16], and positive result for SARS-Cov-2 test in recovered patients[17]. At the same time, some reports discussed some COVID-19 patients with underlying disorders, such as diabetes[18], cancer[19] and so on. As we all know, people around the world should pay attention to this disease.
There are some limitations in our study. First, the number of observed events is to some extent small which may limit the statistical power of this research. However, the sample size is sufficient to draw a conclusion. Second, in our group, there were fewer severe patients which may not balance for analysis. Third, the causal relationship between abnormal laboratory findings and severity could not be estimated since laboratory findings were measured on admission and may not indicate the severity of COVID-19.