Analysis clinical features of COVID-19 infection in secondary epidemic area and report potential biomarkers in evaluation

Weiping Ji; Gautam Bishnu; Zhenzhai Cai; Xian Shen

In patients with COVID-19 infection diagnosed in the main epidemic area, the laboratory examination results at the early stage of the disease showed that the total number of white blood cells decreased or remained normal; the lymphocyte count decreased; the monocyte count increased or remained normal; the liver enzyme, muscle enzyme and myoglobin levels increased in some patients; the C-reactive protein and ESR increased in most patients; procalcitonin remained normal; D-dimer increased in severe patients; lymphocytes progressively decreased; and coagulation function decreased. Inflammatory cytokines, such as interleukin-2, tumor necrosis factor-α (TNF-α), IL-6, and interferon-γ (IFN-γ), remained normal or slightly increased. The level of cytokines in patients with organ failure was significantly increased. In addition, coronavirus nucleic acids were detected in throat swabs, sputum samples, lower respiratory secretions and blood samples [6, 7] . Among the infected patients, the viral load detected in the secretion of the lower respiratory tract was higher than that detected in the upper respiratory tract [9, 13] . The laboratory examination results of the 33 patients showed that the total number of leukocytes in patients with COVID-19 infection in the secondary epidemic area was slightly reduced, normal or slightly increased, and the proportion of lymphocytes in some patients was significantly reduced. Rarely, lymphocytes or neutrophils were increased, and monocytes and eosinophilic acid-base granulocytes were not changed significantly. CRP did not change significantly in all patients with COVID-19 infection, and some patients maintained a normal CRP level, but it was found that serum amyloid A (SAA) increased significantly in most patients that were tested; however, due to the limited amount of data, a statistical analysis was not performed. SAA is an acute-phase protein. SAA significantly increases in viral infection, whereas CRP may not increase or only slightly increase in viral infection without bacterial infection. Moreover, SAA increases in both viral and bacterial infections, and the increase reflects the severity of the infection. At present, it is generally agreed that SAA and CRP should be combined to judge inflammatory activity [14] . Considering that COVID-19 in the secondary epidemic area may occur after the primary epidemic in the main epidemic area, and its toxicity and pathogenicity may be weakened, SAA detection in the secondary epidemic area should be considered to evaluate the occurrence and development of COVID-19 infection. We will focus on the detection of SAA in COVID-19-infected people in follow-up studies. The significant differences in the ratios between various blood parameters and CRP between the two groups are interesting findings in this study. It has been reported that CRP may not increase or only slightly increase in viral infection without bacterial infection, and the increase indirectly reflects the severity of infection. At present, it is generally accepted that CRP or combined CRP can be used to judge the inflammatory activity [15] . In this study, we found that the ratio between various blood parameters and CRP was significantly increased in patients who had indirect contact with the disease in the epidemic area, suggesting that the change in the reactivity of CRP in COVID-19 infection is greater than the response of various blood parameters. In addition, considering that COVID-19 in the secondary