WHY ANTIBODY TESTS CANNOT BE USED TO DIAGNOSE COVID-19 INFECTION YET

Antibody tests for covid-19 are essential in determining who had a covid-19 infection in the past, especially because many people get infected and do not show any symptoms of the virus but can still spread it. However, there is still hope that the rapid covid 19 testing could help diagnose covid-19 as the test would be quicker and less invasive than the current type of testing known as PCR which uses swabs. What makes it difficult is that it is challenging to develop a test sensitive enough to detect the covid-19 antibodies earlier on during the active infection.

About antibody tests for covid-19

The antibody test for covid-19 tells the doctors who had a virus. An antibody is a tiny Y-shaped molecule that binds to antigens on the virus. When they attach to the antigens on the virus, they can stop the virus from getting into the system and replicating.

The human body’s immune system only makes antibodies to viruses one was infected with. Every antibody is different, and one can have various antibodies binding on the same antigen. When someone has recovered fully, the immune system retains some of these antibodies circulating in the blood. As such, if that specific individual gets infected by the virus again, the immune system triggers the production of the antibodies again.

Regarding covid-19 antibody testing, it helps healthcare professionals and governments establish how widespread asymptomatic covid-19 infection is to ramp up covid-19 prevention measures.

Antibody tests for covid-19 are also helping scientists and researchers establish what a good immune response to the covid-19 virus looks like. Although it is an unknown fact, more research is required to develop a fully effective vaccine for the covid-19. To create an antibody test, scientists choose a specific virus and use it in the lab to identify antibodies specific to it of all the antibodies in the human blood. That is to assess how many antibodies against a particular antigen are available in the blood.

Rapid antibody tests work by taking a sample of the patient’s blood through a finger prick. If the blood has antibodies that bind to a specific antigen, the result is positive, and if not, the test result is negative. But for accurate results, the specificity and sensitivity of the antibody test are emphasized.

Antibody tests need to be more specific and sensitive

Antibody tests need to be sensitive to avoid what is known as false negatives whereby the patient’s blood seems to have no antibodies against the SARS-CoV-2 despite a previous active infection of the virus. The antigen selected by the test developer has to be a virus that the body makes a significant number of antibodies against. Therefore, if doctors and scientists want to use rapid antibody tests to diagnose the covid-19 virus, they must make a highly sensitive test.

The specificity of the test is necessary to avoid what is known as false positives. At times, viruses have the same antigens, especially if they have close relations, for instance, the SARS-CoV-2 and the common cold viruses. As such, a test that is not specific as needed may bring a positive result to a different type of virus. The antigen for testing SARS-CoV-2 should be specific; otherwise, someone may turn positive when for covid-19 they are just experiencing a common cold.

conclusion

Until scientists are sure of the sensitivity and specificity of the antigens used to develop antibody tests, they can’t use them to diagnose a covid-19 active infection.