Viral Induced Proteins
As aforementioned, the serology testing of COVID-19 is not targeting the
virus itself but the antibodies such as IgM and IgG induced following
viral infection. These immunoglobulins were serological testing markers
for after the patient has early (3 to 6 days after exposure to the
virus, IgM) and late virus infection (after 8 days, IgG) response
respectively [11]. The serological testing is crucial to identify
active patients, asymptomatic carriers or convalescent persons and
provide population surveillance. These data could be used to analyze and
estimate the SARS-CoV-2 epidemiology and virology [12] and help to
contain the outbreak of the pandemic. The highly reactive human could be
the donor of convalescent serum for therapeutic [13]. The WHO
interim guidance on COVID-19 testing suggested collecting blood, stool
or autopsy materials such as lungs (deceased patients) as serology
testing specimens [7]. As it has been reported that several factors
could contribute to a high false-negative rate (FNR) when using NAAT,
serology testing should also be taken into consideration as alternative
testing or correlation testing [14]. There are companies such as
Guangzhou Wondfo Biotech, China, Innovita Biological Technology, China;
Pharma (Berlin), Germany and RayBiotech Inc. US have released various
types of test kits that specifically testing on COVID-19 IgM and IgG.