Introduction
In December 2019, an unexplained viral pneumonia broke out in Wuhan, Hubei Province, China [1, 2]. The origin of the novel coronavirus remains unknown. However, gene sequencing analysis showed the virus was closely related to the coronavirus detected in wild animals. The novel coronavirus, named the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) by the International Committee on Taxonomy of Viruses, causing the Corona Virus Disease 2019 (COVID-19), termed by the World Health Organization (WHO) [3]. COVID-19 has a lower mortality rate, is more contagious, and has caused a higher death toll than severe acute respiratory syndrome (SARS). These factors have led to a global pandemic within only a few months. At present, the epidemic in China has been well controlled due to a series of effective measures taken by the Chinese government, but it is still spreading abroad. The main challenge faced by the word in the future, in terms of the prevention and control of the epidemic, is the quick and accurate identification of the asymptomatic infection of SARS-CoV-2.
A positive result from a nucleic acid test is important for the diagnosis of asymptomatic patients with SARS-CoV-2 infection. Real-time fluorescence PCR (RT-PCR) is the main method to detect viral nucleic acid. However, the many limitations (i.e. long detection cycle, expensive reagents, and high requirements for sampling, technicians and laboratory conditions) can lead to high false negative rates and the untimely diagnosis and screening of asymptomatic cases. Therefore, there is an urgent need to explore a rapid, simple, and feasible method for the diagnosis and screening of COVID-19.
Serum immunoglobulin M (IgM) antibodies appear in the early stages of viral infection. This is followed by the production of serum immunoglobulin G (IgG) antibodies. These antibodies are essential for long-term immunity and immune memory. Detecting serum IgM and IgG antibodies may provide a valuable detection method for the diagnosis of COVID-19, especially when screening for asymptomatic infection. The aim of this study was to provide evidence for screening infection in asymptomatic patients with COVID-19 through the dynamic analysis of IgM and IgG levels.