Antibody tests have attracted the attention of the whole world, because they may reveal who has been exposed to Covid-19 and who may have been immunized now. This coronavirus test can help to identify asymptomatic and mild infections and avoid the recurrence of the epidemic.
At present, dozens of biotechnology companies and research laboratories have rushed to produce blood tests. Governments around the world have purchased millions of test kits, hoping that they can guide people to decide when to relax from social isolation measures and let people return to work.
Some people even suggest that these antibody test kits can be used as an "exempt passport", so that people with "exempt passport" can interact with others again.
Some researchers say that these tests can tell health care and other basic workers whether they are still at risk of infection. In the future, they can also evaluate whether the candidate vaccine can immunize people.
However, like most new technologies, there are signs that the role of COVID-19 antibody test has been exaggerated. At present, the accuracy of most kits is not enough to confirm whether a person has been exposed to this virus.
Some scientists say that even if the results of using the antibody test kit are reliable, it can't show whether someone is immune to reinfection.
Researchers around the world are also using antibody tests to estimate the infection degree of coronavirus at the population level. In view of the fact that many places have not done enough standard tests, while in the official case statistics, people with mild symptoms or no symptoms are likely to be missed, which is very valuable. These surveys tested a part of the population and used this to estimate the infection situation in a wider community.
When the virus invades the human body, the immune system produces antibodies to fight it. The antibody test kit uses antigen components in the virus to detect the presence of antibodies.
Tests are usually divided into two categories: laboratory tests, which need to be handled by trained technicians and it takes about one day.Isolation point test,it can give quick field results within 15 minutes to half an hour. Health agencies said that these tests did not detect the virus itself, so their application in diagnosing active infection was limited.
Early research on people recovering from COVID-19 has detecting three SARS-CoV-2 specific antibodies, and manufacturers and research institutions have developed testing methods for these antibodies. For example, some biopharmaceutical companies have developed a laboratory test to detect SARS-CoV-2 specific immunoglobulin G and immunoglobulin A.
A high-quality antibody test kit should reach a sensitivity and specificity in 99% or more, which means that there should be only one false positive and one false negative in every 100 true positive and negative results.
Quick and convenient tests are even less reliable than those used in the laboratory. This is because they use smaller blood samples, they are usually blood samples from stab wounds and they are conducted in a more uncontrolled environment than in the laboratory, which will affect their performance. They should use COVID-19 antibody test kit with caution. WHO recommends that the isolation point test should only be used for research purpose.
An unknown factor affecting these two tests is the interaction between time and accuracy. If a person is tested too early after being infected, and the body has not yet produced the antibody to be tested, it may miss the infection.
However, scientists still don't know the time of human immune response to SARS-CoV-2, so they can't tell exactly when the specific antibody was produced.
To sum up, after the COVID-19 antibody test kit is finished, the results should be carefully analyzed, and the most important thing is the contact history, and the suspicious performance should be tested for many times before the real purpose can be achieved.