Experts agree that for normal activity to be restored in society, it is key to identify individuals who have the coronavirus infection and the ones who have recovered from the disease. These people can only be identified through a special kind of test, called ‘serological test’.
The Need for Serology Tests
Widespread serological coronavirus testing is aimed at finding people who got sick with coronavirus very mildly, took it for something else, and even people who got the virus and were completely asymptomatic. These people’s immune system must have generated a lot of antibodies in response to the infection.
As experts believe that reinfections are unlikely in coronavirus patients who have recovered, this phenomenon can be used to modify public heath response.
Tim Searchinger et al explain we have one clear way to fight the disease and save our economy: a regime of massive testing of our population, using the PCR and serology tests. Congress must build this into our package this week. https://t.co/fx9g2E7xgI
— Rep. Jamie Raskin (@RepRaskin) March 24, 2020
These serological tests will differentiate people who have had the infection (not at risk anymore) and those who did not (more at risk). This will enable people who work in health care, essential services like food and medication supply chain, and volunteers, to return to actively fight and control the disease. Such people can help treat coronavirus patients, provide services to those stuck inside their homes, and people who have compromised immune systems.
— Arturo Casadevall (@ACasadevall1) March 31, 2020
Identifying how much population is still at risk will also help policymakers with decisions like when to lift stay-at-home orders, resuming businesses and reopening schools. The sooner the facts are clearer, the sooner the life can return to normal.
Several factors will have to be considered before these tests can be used at a massive scale, like ensuring availability of millions of accurate tests, and answering questions, like what level of antibodies are enough, how long immunity will last, what timelines would be best to deploy these tests to ensure no one is missed out, how privacy of people can be protected, and how people will declare their immunity status. All of these questions need to be answered for this to work.
— Arturo Casadevall (@ACasadevall1) March 31, 2020
These tests can also be diagnostic and provide quicker results. The currently used test for diagnosing coronavirus patients is a real time PCR (RT-PCR). Those tests are time consuming with a turnaround time from hours to sometimes days, depending on the volume of tests being performed.
Understanding Serology Tests
To understand how these tests can help, let’s first understand what these tests are and how they work. Serology tests are blood-based tests. Scientists use these tests to see if the blood of a person has been exposed to a specific pathogen or a virus. For example, if you want to see if you have had the coronavirus infection or not, a lab technician will withdraw your blood and analyze the serum component of your blood.
Human body produces antibodies in response to any invading pathogen in the body. Same happens with the coronavirus. These antibodies are very specific to a microbe. Your blood serum contains these antibodies. Scientists can easily distinguish between different antibodies in the body.
Through serological testing the scientists will be able to identify whether you have an active infection, or if you have had the infection in the past. There are numerous types of these tests such as neutralization assays that check for functional antibodies, immunofluorescent assays, enzyme linked immunosorbent assays (ELISAs) which provide rapid results, and western blot tests.
For coronavirus, experts believe two of these tests can be used. First, the western blot test to detect coronavirus in the blood and ELISA test that can detect patient’s antibodies to the virus.
New Diagnostic Serological tests
BD, a medical technology company and BioMedomics, a clinical diagnostic company in North Carolina, both have announced new rapid serological tests. These rapid tests can detect exposure of coronavirus, both present and in past, within minutes. The tests developed by BD can detect antibodies within 15 minutes.
— BD (@BDandCo) March 31, 2020
— BioMedomics, Inc. (@BioMedomics) March 9, 2020
Abbott has also announced a rapid test that can provide positive results in under 5 minutes and negative tests in 13 minutes. Researchers at Mount Sinai Health System have also announced development of such an ELISA test that can identify both active and previous infections.
— Abbott (@AbbottNews) March 27, 2020
These tests can be used to rule out COVID-19 infection, if used after a few days of symptoms. However, as effective as these tests may be in identifying patients, the US Food and Drug Administration (FDA) advises that this method should be used in conjunction with RT-PCR to identify active infections. These tests can be distributed without regulatory approval because the FDA has relaxed the rules during the public health emergency, but these antibody tests have to be clearly labeled as not approved by the FDA.
The Food and Drug Administration denied that it has approved any serology tests, even in an emergency fashion, for the coronavirus.https://t.co/AuGXx8042L
— Washington Examiner (@dcexaminer) April 1, 2020
Serological Testing to Aid in Plasma Therapy
Serological testing will also be beneficial for plasma therapy. A highly experimental treatment called convalescent plasma therapy is being developed around the world, to fight this pandemic along with regular drug therapy.
This convalescent plasma therapy can use blood from people who have already been infected and recovered. The blood from such people can then be used to separate antibodies generated against coronavirus, and the be given to people who are infected right now. Rapid antibody or serology testing will help identify individuals with previous exposure quickly.
The theory is that these antibodies can provide protection against the virus in infected individuals and also reinforce their immune response. Whether this therapy will work or not, or whether it can be amped up for massive public use, is yet to be seen.
FDA is encouraging researchers to begin clinical trials to test applications of plasma therapy and has even allowed its experimental use, owing to the need of the hour.