Nucleic acid testing of the virus has been the primary method of detection since the onset of the New Coronavirus outbreak. Initially, our scientists conducted specimen collection through nasopharyngeal swabs for virus detection, but with the continuous in-depth research and understanding of the new coronavirus, it was found that in addition to nasopharyngeal swabs, sputum and other lower respiratory secretions, blood, stool and other specimens can be detected in the nucleic acid of the new coronavirus. So some people may ask, why is neo-coronavirus not detected by blood test?
The role of blood test in neo-coronavirus detection
No matter what the disease is, blood test is an essential test in clinical treatment. If a patient has a normal or reduced peripheral blood white blood cell count and a reduced lymphocyte count, then it is likely to be a viral infection, and then combined with the patient's epidemiology and signs and symptoms, the doctor will be able to determine whether the patient is a suspected case of neo-coronavirus infection, and only then will there be a follow-up viral nucleic acid test.
So in this respect, blood tests are also helpful in screening for neo-coronavirus.
If we are to say that blood testing is used for neo-coronavirus nucleic acid testing, it is not the preferred method of testing in the early stages of the outbreak. This is mainly due to the mode of transmission of the new coronavirus. As we all know, the new coronavirus is transmitted mainly through droplets and contact, and the presence of ACE2 receptors in the respiratory tract, which are necessary for the invasion of the new coronavirus, makes the respiratory tract of the infected person the main gateway for the invasion of the new coronavirus, and therefore the infected person will often be complicated by pneumonia.
Therefore, in the early stages of infection, nasopharyngeal swabs, sputum and other lower respiratory secretions are the preferred specimens for viral nucleic acid testing in suspected cases, and these specimens have the highest rate of positivity. In contrast, blood nucleic acid testing at this time is likely to be negative because the blood is likely not yet invaded by the virus in the early stages of infection.
Conclusion:
It is interesting to note that one of the major changes in the latest version of the treatment protocol is the addition of serological testing for neo-coronavirus specific antibodies IgM and IgG as part of the evidence to confirm the diagnosis of neo-coronavirus infection, but this IgM also starts to appear positive 3-5 days after the onset of the disease. In conclusion, however, it is currently possible to detect neo-coronavirus by blood, but blood specimens are not the preferred specimens for viral nucleic acid testing.
