COVID-19: What Is Antibody Test & How Is It Different From PCR?
Antibody tests can detect old cases of coronavirus infection including the ones that were not diagnosed.
In order to ramp up the coronavirus tests, India is now taking a cue from South Korea which has managed to flatten the curve by taking various unique measures including the one to perform more antibody tests.
Last week, the Indian Council of Medical Research (ICMR) invited tenders for 5-Lakh antibody testing kits for the diagnosis of COVID-19.
So far, India has only been relying on genetic tests which are time consuming and expensive. Known as PCR test or polymerase chain reaction tests, these don't have the ability to detect old cases of coronavirus. On other hand, antibody tests are quick and can detect a case of past infection.
What Are Antibody Tests?
Antibody tests or serological tests are conducted by taking the blood sample of a person. Our immune system produces antibodies to neutralise the viruses in the body. These antibodies remain inside us for a considerable amount of time - even after the infection generated by the virus is completely gone. This helps doctors to recognise whether the patient was earlier infected or not.
A patient who couldn’t get tested earlier or self-recovered can be identified with the help of this test. This can give the government a clear estimation of how much of the population is actually infected or was infected.
How is Antibody test Different From Genetic Tests?
For the real-time PCR tests, swab samples of a patient are collected whereas, for serological tests, blood samples are taken to identify if the antibodies are present in the blood.
Swab samples are based on RNA which means they help find evidence of the virus’ RNA genome in a patient's body. As the patient recovers, RNA can't be traced.
Thus, PCR tests can't recognise if a person was infected by novel coronavirus earlier, but serological tests can do that. At the same time, PCR tests are time consuming, complicated and expensive in comparison to serological tests. However, it is important to note that if the samples are tested early, both of these tests can fail to detect the virus.
What Does ICMR Guideline Say?
A guideline related to antibody kit released by ICMR on 27 March says, "Positive test indicates exposure to SARS-CoV-2. Negative test does not rule out COVID-19 infection."
It further says, "not recommended for diagnosis of COVID-19 infection.” This essentially means that the ICMR still relies on genetic tests for diagnosis, however, to identify old infection, serological tests will be hugely beneficial.
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