In a molecular virology unit at a hospital in Italy. (Photo via AP)
On Wednesday, the Indian Council of Medical Research invited bids for an estimated 10 lakh antibody kits (for serological tests) for the diagnosis of COVID-19. The kits have to be supplied to 6 locationsâ€“ Dibrugarh, Mumbai, Chennai, Hyderabad, Bhopal, Delhi, and need to be FDA/CE IVD/NIV Pune certified.
What are serological tests?
Viral infections are mainly identified by two kinds of testsâ€“ genetic and serological. Genetic tests can identify infections that are active, but cannot be used to detect past infections. To trace how infections like the novel coronavirus have spread so far, it is important to detect people who contracted the disease in the past and have recovered. This is what serological tests seek to determine.
How are the two different?
The genetic test is conducted on a swab collected from the back of the throat, a liquid sample from the lower respiratory tract, or a simple saliva sample. For SARS-COV-2, the virusâ€™s RNA is first converted into DNA. By a process called polymerase chain reaction (PCR), DNA fragments in the sample are copied exponentially -- one is copied into two, the two are copied into four, and so on.
Unlike genetic tests, which look for RNA in swab samples, serological tests work on antibodies in blood samples. Hence, they are also called â€˜antibody testsâ€™. Antibodies, or protective proteins produced by the immune system to neutralise pathogens such as bacteria and viruses, are present in oneâ€™s bloodstream for a considerable period of time after the infection has gone.
ðŸ“¢ Express Explained is now on Telegram. ClickÂ here to join our channel (@ieexplained)Â and stay updated with the latest
To disable a pathogen, the antibody latches to a unique protein molecule on pathogenâ€™s surface, called an antigen. Serological tests use antigen molecules to detect the presence of antibodies relevant to the infection. Generally, a blood sample is placed in a test tube that is lined with antigens on the inside. If the relevant antibodies are present, they latch on to the antigens.
Such tests are relatively inexpensive, and can display results within a few minutes.
Hereâ€™s a quickÂ Coronavirus guideÂ fromÂ Express ExplainedÂ to keep you updated:Â Are smokers at high risk form coronavirus?Â |Â Can Vitamin-C prevent or cure coronavirus infection?Â |Â What exactly is community spread of coronavirus?Â |Â How long can the Covid-19 virus survive on a surface?Â |Â Amid the lockdown, what is allowed, what is prohibited?