Medical resources were in short supply during the COVID-19 pandemic. Hence classified management and treatment of admitted patients will potentially save substantial manpower and material resources leading to improved medical efficiency. It is extremely important to accurately assess the progression of the patient's condition through limited admission data.
Although there were many clinical reports on COVID-19, there was no systematic analysis report on admission assessment. The analysis of antibody levels and clinical characteristics of 1951 COVID-19 patients in this study shows that the overall age of the patients was normally distributed, with the peak value at 61 to70 years old, considering the age distribution characteristics of the normal population, it could be seen that the incidence of COVID-19 conforms to the characteristics of susceptibility to the elderly, which was consistent with previous studies. It has been reported that men were more susceptible to COVID-19, but the sex ratio of COVID-19 patients in this study was close to 1:1, and there was no statistical difference in the COVID-19 infection rate of different genders, but men were more likely to experience aggravation of the disease than in women. It was worth noting that the proportion of male patients with COVID-19 in the 21–40 age group was significantly higher, which might be related to the irregular dietary habits, sub-optimal lifestyle and stresses in males of this age group; as for the 71–80 age group, the proportion of males was also relatively higher, which may be related to weaker immunity of males in this stage. In addition, although the proportion of men and women in the 81–100 age group was similar, given that there were more women in this age group, older men might be more susceptible to the disease. Interestingly, the proportion of COVID-19 female patients in women from the 51–60 age group of was significantly higher, which may be related to the relatively low immune function of women at this stage of due to menopause. However, when compared with gender of patients, age has a more obvious influence in the degree of disease with severity gradually worsens with age.
Although the severity and pathogenicity of patients infected with COVID-19 were not as serious as SARS virus, the patients with other chronic diseases before infection would get worse(deteriorate) and even become fatal after infection. Such common diseases include cardiovascular diseases, diabetes and hypertension, etc., in which patients with hypertension and diabetes usually needed to be treated with Angiotensin Converting Enzyme(ACE) inhibitor or Angiotensin Receptor Blocker (ARB), but these two drugs both lead to an increase in the expression of ACE2, the key guidance factor for COVID-19 to invade the body of patients where the up-regulation of ACE2 expression will lead to increase susceptibility of COVID-19, and then aggravate the disease . The recognition and combination of SARS-CoV-2 and ACE2 could promote the expression of angiotensin II, which induced inflammatory factors and vasoconstriction, and promoted organ damage and stroke which was another poor prognostic factor for COVID-19. Anemia and hyperlipidemia were also important fatal factors. Anemia not only leads to an increase in ferritin and inflammation of the body, but also leads to insufficient oxygen supply, eventually leading to multiple organ failure. In addition, limited studies showed that hypoalbuminemia was also an adverse factor for COVID-19. Our analysis showed that common diseases such as hypertension, diabetes, stroke, hypoalbuminemia and anemia could aggravate the condition of patients with COVID-19, which were important factors to evaluate the prognosis of patients with COVID-19. However, atherosclerosis, Alzheimer's disease, liver disease, COPD and cancers had no obvious effect on the disease. The main reason was due to the minute number of cases. In this study, there were 6 patients with rheumatic diseases (3 severe and 3 mild cases), and 3 with systemic lupus erythematosus, including 2 severe cases and 1 mild disease, although the above data could not be statistically analyzed. However, these two diseases tend to aggravate the condition of patients with COVID-19. Because elderly patients account for a higher number in those with the above diseases, the prognosis of elderly patients with COVID-19 infection might be worse.
Presently, it is considered that IgM was the first line of defense for adaptive immune response after virus infection, and although IgM was produced earlier than IgG, it was the latter which provided long-term immunity and immunological memory. Therefore, IgM antibodies produced in the early stage of virus infection could indicate current or recent infection, while IgG antibodies were an important antibody produced by the immune system. The appearance of IgG in patients means that the disease was in the middle and late stage or has a history of infection. Therefore, the combined detection of IgM and IgG was not only used for the early diagnosis of infectious diseases, but also for the evaluation of infection stages. In theory, adaptive immunity was the best way to deal with all types of infections. The good contribution of innate and adaptive immune response could quickly control the virus and eliminate infectious particles in the body. Antibodies played an important role in virus neutralization, Fc receptor-mediated phagocytosis, antibody dependent cytotoxicity (ADCC), complement dependent cytotoxicity (CDCC) and subsequent pathogen clearance. However, ADCC and CDCC could cause harmful systemic pro-inflammatory response, resulting in serious pathophysiological consequences. The disproportionate immune response can lead to virus transmission, multiple organ failure and high mortality. At present, there were still debates whether antibodies in COVID-19 patients activate protective or destroy the immune response of the host. Compared with the contribution of host antibodies in COVID-19 patients to resist and eliminate the virus, people paid more attention to the correlation between the level of SARS-CoV-2 antibody and the disease severity of patients with COVID-19. Although it had been reported that the weak correlation between antibody titers and neutralizing activity in COVID-19 patients, some literatures showed that IgG and total antibody levels of hospitalized patients were positively correlated with disease severity, and positively correlated with the patient's age and gender. This phenomenon can explain that severe COVID-19 infection was more common in elderly men. Hansen even pointed out that the antibody concentration, especially the IgG level, was related to specific symptoms such as fever, sore throat, shortness of breath and nausea. The SARS-CoV-2 antibody response determined the disease severity of patients infected with COVID-19 . The unnecessary immune response to SARS-CoV-2 might be one of the mechanisms leading to overactive macrophages and monocytes, leading to a fatal cytokine storm, which seemed to be a marker of COVID-19 . Nevertheless, some studies have shown that low IgG levels in COVID-19 patients were associated with poor prognosis of severe and critically ill patients. This conclusion was partly consistent with the results of our analysis. Our study of 136 patients with COVID-19 with low IgG and IgM concentrations showed that most of the patients with low IgG and IgM concentrations were male patients aged 20–40 years old, and the low expression of antibodies was related to the poor prognosis of patients with severe and critical diseases, the severity of disease was closely correlated (p = 0.061); In addition, 136 cases of COVID-19 patients with low IgG and IgM were analyzed in different age groups. The results showed that the proportion of patients with severe diseases in the age group of 21–40 years increased significantly, the proportion of patients with severe diseases in the range of 41–60 years was relatively reduced, and the proportion of patients with severe diseases in the 71–80 years old group increased again. This contradiction in different age groups may explain the phenomenon that some studies have reported that COVID-19 antibodies have made the disease worse. This contradiction itself explains the complex evolution of antibody levels and diseases: On the one hand, continuous viral infection will lead to the consumption of antibodies and thus the decrease of antibody levels. On the other hand, the virus itself was the raw material for stimulating the immune response, and the antibody level often reflects the degree of immune response. Although low antibody concentration did not necessarily aggravate the disease, the expression levels of IgM and IgG in critical illness were significantly lower than those in mild or severe patients. Consistent with our analysis of 265 patients with high IgG concentration, the results showed that although the proportion of patients with mild illness increased and the proportion of patients with critical illness decreased in patients with high concentration of IgG, this phenomenon was consistent with the overall low level of IgM and IgG in critically ill patients, which further illustrated the duality of the effects of high concentrations of antibodies. Although there was no case data of children aged 0–10 years in this study, we detected the antibody concentration of children aged 11–20 years. The results show that the IgG level of COVID-19 patients in this age group was the highest than that in other age groups, which may also be an important reason for the low infection rate and high cure rate of juveniles with COVID-19. These results suggest that high concentration of COVID-19 antibodies tends to benefit patients.
In view of the limited medical conditions and insufficient knowledge of the SARS-CoV-2 virus in the early stage of the COVID-19 outbreak, this study itself had many shortcomings. For example, most patients admitted to Wuhan Huoshenshan Hospital were admitted after a period of infection. Case analysis showed that most patients admitted to Huoshenshan Hospital had been sick for nearly one month, there might be more asymptomatic and mildly infection in patients, while there were relatively few severely and critically infected patients. As a result, some results of this study may be inconsistent with other reports; In addition, in view of the short half-life of IgM, there was only a slight correlation between IgM and IgG in this study. A separate analysis of the correlation between low IgM and disease prognosis might be of little significance; Finally, due to the limitations of experience and conditions, the 1951 patients in this study lacked biochemical testing such as interleukin 6 (IL6) and C-reactive protein (CRP). If these indicators could be detected at the same time, it might play a more accurate role in guiding the prognosis of COVID-19 patients.