It is the best way forward to combat the spread of Covid-19
It is welcome news that the government may finally approve rapid antigen and rapid antibody testing for Covid-19 detection and make them available as early as this month. Given that Bangladesh has entered the sixth month of this pandemic and our testing capacity is limited to 12,000- 14,000 per day with a test positivity rate of 21%, it is high time to avail the alternative cheaper options that are already available and being done in other countries.
What are the issues with the standard RT-PCR test?
Firstly, the gold-standard RT-PCR has a false negative rate as high as 20%, which means 20 out of 100 people may actually have the virus even when the test says otherwise. On the flip side, the extreme sensitivity of the RT-PCR means that it may show someone as Covid-positive when in fact they are no longer shedding enough virus to be infectious to others.
The standard protocol so far is to quarantine everyone who came in close contact with the diagnosed infected person over a period of two weeks, and test them when they show symptoms. The reality is, not everyone who comes in contact will catch the disease or even if they do, they may not show any symptoms. As we reopen our economy, this quarantine protocol will make it impossible to run any operation, office, factory, service industry, or educational institute.
The final factor is the RT-PCR test itself; it is highly uncomfortable and extremely expensive, it requires well-equipped laboratories, highly skilled technicians, multiple reagents, and the results take anywhere from several hours to several days to arrive.
What are rapid tests and why are they game changers?
The rapid antibody test detects prior infected cases with immunity. Its advantage is that it can show you who has already had the disease and produced enough of an immune response that they may no longer be able to be infected. Right now, there is no easy way to know who has produced antibodies against the disease. They are also easy to perform at home, just like the diabetes prick test.
The rapid antigen test detects an active infection while it is infectious. The advantages of rapid antigen tests are multiple: They produce results within thirty minutes, they need only saliva/spit or nasal swab, and there is no complex laboratory equipment or specially trained personnel needed.
Many brands have come up with these kits with 98-99% accuracy. If these rapid kits are made available to homes or institutions, then measures can be put into place for safely opening our economy.
Let us imagine a scenario where a factory that employs 2,000 workers has reopened and has set up a protocol of regularly testing their workers. Initially, they screen everyone with both rapid antigen and rapid antibody testing. They detect that 400 workers already have antibodies against Covid-19 and 50 people came positive from the rapid antigen test.
Those 50 infected workers are then sent into isolation. After 14 days, the rapid antigen test is repeated on those same workers for further screening. Meanwhile, the 400 people detected with antibodies can, for all intents and purposes, be considered safe and can continue working without further testing for at least the next six months. These people can safely rejoin work and if required can be donors for convalescent plasma therapy for critical patients.
This factory can routinely perform these cheap rapid antigen tests on the remaining employees every three days to detect new infections.
What has held us back from embracing rapid antigen tests?
The main argument has been that rapid antigen tests are less accurate and less sensitive than the “gold standard” RT-PCR. This is true. However, when administered virtually every day, the test does not need to be as sensitive. The rapid antigen test comes positive when the person has high viral loads -- and is the most infectious to others. Studies are now showing that people do not spread the infection to others when the viral loads are low.
Daily testing enables people to know within 30 minutes whether they are infected, irrespective of symptoms. Once detected, the risk of infected persons transmitting to others will be lower as they can immediately quarantine themselves. Regular rapid antigen testing will also diagnose cases early on at the viral phase which will prompt monitoring of symptoms to head off the more severe outcomes.
What is our responsibility in protecting ourselves?
Covid-19 is a new disease and there will be new discoveries about it every month. One such discovery was stated in an open letter sent to WHO by 239 scientists from 32 countries. They claimed that evidence shows Covid-19 is not transmitted mainly through droplets or fomites but is actually airborne. They emphasized that the virus remains suspended in air for a long time; the longer an infected person is in a particular space, the concentration of virus will build up in the air surrounding him/her.
Transmission is key for SARS-CoV-2 virus spread. Until and unless a vaccine or a targeted treatment is invented, we must continue with the non-medical countermeasures to prevent its spread. We must continue avoiding public gatherings, and if we have to be out in unknown gatherings, then we must wear masks at all times, maintain six feet distance, ensure windows are open with proper clean air circulation, and maintain handwashing.
Bangladesh is not a social welfare state. Continuing lockdown is not an option when the lion’s share of our people are employed in the informal sector. Having said that, currently we are in the midst of community transmission of the disease. Rapid testing will be a cheaper option to lockdowns, institutional quarantine, and contact tracing. Cheap, easy, and rapid antigen tests are the key that will allow us to open our businesses, our schools, and our places of worship and begin to see light at the end of the tunnel.
Dr Maliha Mannan Ahmed is the Founder and Executive Director of Organikare. She has an MBBS, MBA, and a Masters in Healthcare Leadership.