On December 31, 2019, when reports of a mystery virus leaked out of China, scientists raced to develop lab tests that would detect the unknown entity. By January 16, the world’s first test was unveiled. The man who led the research was German virologist Christian Drosten, famous for designing the Zika, MERS and SARS tests earlier. As his protocols were made public, to guide labs across the world, Drosten said: “Now that this diagnostic test is widely available, I expect it won’t be long before we are able to reliably diagnose suspected cases.”
That hope has not quite worked out. And even as widespread testing emerges as the backbone of the global war on coronavirus pandemic, there is an uneasy sense that the virus might be outsmarting the test-kit. Questions are rising faster than they are being resolved: how robust, reliable and resilient are the tests? The World Health Organization (WHO), which declared, “We have a simple message to all countries—test, test, test,” on March 16, has now warned against relying on tests for policy decisions. A new question is growing ever more urgent: is more testing always better?
Not testing enough
“Why is India testing so little?” The “callousness” of India’s COVID-19 response drew global censure, as international media speculated if the number of Indians infected with coronavirus was actually much higher. The most responsible reports came from science journal Nature: “Without enough test kits, the 1.3-billion-person country is using a gigantic surveillance network to trace and quarantine infected people.”
The report compared India with countries such as South Korea that were using widespread testing, adding that India’s mass-surveillance approach could achieve the same results and be an example for other low- and middle-income countries facing kit shortages. Yet with the domestic media screaming, “test, test, test,” India changed its policy, issuing licence to import test kits, at an estimated cost of `100 crore in the first installment.
Too slow, too narrow
Scientists believe testing to be a window to the pandemic—how it is spreading, what risks it poses to different populations, which interventions should be implemented where and what countermeasures are working, or not. Testing is also seen as a possible way to get out of costly economic measures like lockdowns.
The current gold standard test for COVID-19, the polymerase chain reaction (PCR), is taken via nose, throat, sputum and lung swabs and takes several hours to detect genetic traces of the virus. That makes it too slow in a pandemic situation. It also detects only active infections in patients. That means, it cannot identify people who may have been infected earlier and recovered. Hence, PCR tests do not help us understand the full extent of the pandemic spread.
Hunt for a game-changer
A host of diagnostic companies and labs around the world are now focusing on smaller, simpler and rapid testing kits that can be brought closer to patients and give results in minutes. Finger-prick tests, they work on blood samples. And they don’t look for the virus, but for antibodies—or proteins produced by a patient’s immune system in response to the virus. Not just simple and fast, the beauty of these tests lies in the fact that our immune cells can remember infection-causing invaders, to spot and destroy them in future. So long they remember, we stay immune to that infection.
These tests, therefore, are simple and rapid enough to be used for mass testing; they can detect immunity among healthcare workers, enabling them to carry on with their work; they can give a boost to people on the frontline—police officers and other essential workers; they can identify people who have developed immunity and can return to work, kickstarting the flagging global economy; those with immunity can also donate blood to high-risk and seriously ill COVID-19 patients, to boost their ability to fight the virus—a line of treatment known as “convalescent plasma therapy”.
Problem of false results
As hundreds of tests come on the market and more people get tested, concern about their accuracy grows. Current coronavirus tests seem to have a particularly high rate of missing infections. In fact, no test seems to be 100 per cent accurate. They can generate “false negative” results, or show that you do not have the infection when in fact you do. Or they can be “false positive,” showing that your body has developed infection when it hasn’t.
In PCR tests, inaccuracies creep in depending on the severity of the illness, when the samples were taken and how the swab was done. A patient in early stages of infection, or with inadequate specimen collection, may show up as negative. Antibody tests are generally far less sensitive than PCR tests: they are not good at diagnosing infections early, when the body’s immune response is still building—often five to 10 days after infection. And they often do not pick up milder infections.
A smart virus?
Across the world, people with signs and symptoms of COVID-19 are testing negative. Others with no symptoms are testing positive. Yet others are getting infected a second time. Are the tests that unreliable or is the virus too smart?
One difficulty with tests is that most of these lack data to back them up. The demand for rapid, point-of-care tests has led a host of private companies, as well as governments, to launch test kits in a hurry, but how accurate they are remains to be seen. There is suspicion that some of the tests may not be able to tell the difference between different types of coronavirus (one-third of common colds also belong to the coronavirus family).
One big question is about the new virus: crucial details about how it works and spreads are still unknown. Some researchers are worried that the virus is mutating so it can spread more efficiently. In the space of a few months, there has been a massive rise in infections spreading from people who do not show any symptoms—or asymptomatic transmission. From causing severe illness mainly in older people, the virus is now also affecting younger people. It is now clear that the virus can hide symptoms for over 24 days, and not just two weeks. Cases of reinfections are rising, but exactly why remains unclear. Is it because the virus is mutating into new strains and infecting again, or is it hiding in cells and reactivating later?
No magic pill
Until the unanswered questions are solved, it would be a mistake to rely on mass testing as the key tool to beat coronavirus with. Countries that received early praise for success in handling the pandemic through high levels of testing—Germany, South Korea, Singapore—are now lagging behind, with the number of patients testing positive twice rising steadily. Public health officials around the world are scratching their heads: is it reinfection, reactivation or inconsistent testing? Headlines are changing once again: “We may need to think bigger.”