At a time when the Indian government is exploring ways to ease the lockdown, serology tests are expected to play an important role by considerably improving the pace of testing.
India is currently testing people with real-time reverse transcription polymerase chain reaction, or RT-PCR method, which is reliable, but is expensive and difficult to scale up.
The Indian Council for Medical Research (ICMR) - the apex medical body that is crafting the government's policy and coordinating efforts - said it has ordered five lakh antibody test kits, of which 2.5 lakh will be delivered in the coming week. ICMR plans an aggressive serology testing in novel coronavirus, or COVID-19, hotspots.
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What are serology tests? Serology tests are blood tests that track down antibodies, which are created by the immune system for fighting off a disease. Antibodies can be particular for one kind of disease and provide a window into a patient's infection history. They are useful to understand whether a patient has a COVID-19 infection or not.
They are two types of serology test - one tests for viral proteins that bind with antibodies and helps in detection. The second is an ELISA (enzyme-linked immunosorbent assay) test that detects the patient’s antibodies to the virus. ELISA is not scalable like RT-PCR test as it requires labs and instrumentation. The ones that ICMR is talking about is the rapid antibody test kits.
Rapid antibody test kits Rapid antibody test kits are similar to home pregnancy kits. They just need two drops of blood from a pinprick to detect a virus. It takes 15-20 minutes to get the result. The test detects both immunoglobulin (Ig)M and IgG antibodies. The immune system produces IgM antibodies in the initial stages of infection and IgG at later stages. It doesn't require expensive instrumentation, biosafety level-3 laboratories and trained people. The main advantage is they can be mass produced, relatively less expensive and easy to self administer.
How will they help in easing the lockdown? Rapid antibody-led testing is easy to deploy and helps to scale up testing. Till date, around 84,739 tests have been conducted in India. Results indicate nearly 3,349 people have been infected thus far and 83 have died as of April 5. The testing capacity of government labs is about 13,000 per day. Many Indian companies have started developing rapid testing kits and are in the process of getting validation from ICMR. Some have already got approvals. People, who have positive antibody tests, can be allowed to go back to work, while following social distancing. For instance, Germany and UK are considering 'immunity certificates' for people who have positive antibodies.
How accurate are rapid antibody tests? While there is a fair degree of comfort with RT-PCR test as they are widely used. The accuracy and reliability of rapid antibody tests will be known once they are deployed. There could be problems of false-positives, if the test detects antibodies produced in response to coronaviruses other than COVID-19. There are still lot of unknown things about COVID-19.
Information like how soon after infection do patients develop antibodies against COVID-19 and how long do COVID-19 antibodies last in the body.
Some reports suggest that it's possible certain number of people get re-infected by COVID-19. Also the quality of test kits is another issue.
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