New Delhi: Over the past two days, the Indian Council of Medical Research (ICMR) sought quotations for the supply of 15 lakh antibody kits that are used for serological testing, as part of the diagnosis for Covid-19. These kits could now be used for research, surveillance and investigation purposes. They can be used on persons who have already tested positive for the virus or even those who are asymptomatic and can reveal insights on immunity against Coronavirus.
Detecting tell-tale antibodies in the blood will help identify the real number of people in a population who have ever come in contact with the virus. Over the coming months, the results will determine everything from how long the shutdown needs to be, to evaluating the effectiveness of the new vaccines on the horizon.
News18 explains what these tests are:
What are serological tests?
According to John Hopkins Bloomberg School of Public Health, they are blood-based tests that are used to identify if any person has been exposed to a particular pathogen. As part of these tests, the serum of the whole blood (the part that does not contain white and red blood cells) is analyzed as it contains antibodies that the body produces to fight pathogens, called antigens. Antigens are foreign substances which are recognized by the immune system and are targeted with an immune response.
The serological tests are used during viral infections to see if the patient has an immune response to a pathogen, such as influenza, a fact sheet of the John Hopkins Bloomberg School of Public Health stated. Using these tests, an infection can be used to diagnose an infection.
Why were the kits not procured earlier?
Across the world, the Real-time polymerase chain reaction (PCR) based test has been the primary testing method to confirm positive cases of Covid-19. Serological tests are not used for confirming the Coronavirus infection. Globally, there was dearth of these kits and a race is on to develop such kits. It is still not clear how many companies in India are capable of producing antibody kits.
How are they different from diagnostic tests currently used to detect Covid-19 cases?
Currently, Indian labs are using the real-time PCR based tests to confirm Covid-19 cases. As part of these tests, nose and throat swab samples of the suspected patient are collected for a genetic test whereas for serological tests, blood samples are taken.
Real time PCR tests will not reveal if a person was affected by the infection if he or she has recovered or even if a person has not developed symptoms. Meanwhile, a serological test can determine if a person was infected even after he has recovered, based on identification of antibodies. Both methods may also miss detecting a positive case if the sample is collected too early.
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