Covid-19 tests that can facilitate widespread screening and help limit the spread of the disease are fundamentally different from the diagnostic tests currently being used. Pre-pandemic, diagnostic tests were designed to be used on symptomatic individuals, did not need to be low cost, and required high sensitivity to return a definitive clinical diagnosis with the test being taken only one time. In contrast, Covid-19 surveillance to reduce the population prevalence of the virus, which involves testing large portions of the general population whether symptomatic or not, requires diagnostic tests that return results quickly, are inexpensive, and easy to execute to enable testing of individuals multiple times in a week.
Currently, the gold standard of Covid-19 diagnostic testing is to use the polymerase chain reaction (PCR) tests. However, PCR tests are not traditionally used for surveillance as they are infrastructure-greedy. After collection, the patient sample is transported to a centralised lab where specific laboratory equipment and trained personnel increase the cost of the test and also pose an inherent testing capacity limit. Turnaround times for test results can take one or more days, which can be too long during a pandemic when limiting the spread of the disease is of the utmost importance. PCR tests are much more suited as a confirmatory test to confirm a diagnosis based on symptoms. Over the course of the pandemic, it can be seen that the scaling up of PCR tests to a national level has been difficult to implement around the world with many countries still far below the number of tests recommended by the World Health Organization (WHO) and other health organisations to adequately capture the extent of the spread of Covid-19. In June, the Centers for Disease Control and Prevention (CDC) estimated that there were ten times as many Covid-19 cases in the US as had been detected. So even though the PCR tests being used to diagnose Covid-19 are highly sensitive, using PCR tests alone is not enough to limit the spread of the disease.
For an effective measure that will stop the pandemic, tests are needed that are fast, inexpensive, and accessible to the largest number of people (that is, at-home testing). This test already exists, in fact, it is a rapid lateral-flow antigen test, which employs technology similar to at-home pregnancy tests. Such tests are cheap, for example, the Abbott BinaxNOW is just $5 and can return results in 15 minutes. These tests can be produced in the tens of millions or more per week, can be performed at home, and open the door to effective Covid-19 surveillance.
Importantly, rapid Covid-19 antigen tests are not here to replace PCR tests but to serve as the first line of defence and to complement PCR tests. The Food and Drug Administration (FDA) emergency use authorisation of antigen tests states that if a symptomatic patient receives a negative test result from an antigen test, they still require a PCR test to confirm.
GlobalData predicts that the Covid-19 testing market will continue to grow and antigen tests will play an important part in that growth. As the Covid-19 vaccine is developed and becomes widely adopted, Covid-19 testing will remain one of the most important tools for monitoring spread and eventually containing the disease.