The World Health Organisation has made it very clear that, in order to stop the spread of COVID-19, we need to “find, test, isolate and care for” those confirmed infection cases and also put the close contacts of those confirmed cases into quarantine for the 14-day incubation period of the virus. However, most countries still do not have the COVID-19 testing capacity required to implement these guidelines. Importantly, even though many countries are now recovering from the infection peak, the latest studies point out that we may experience recurrent wintertime outbreaks of COVID-19 after this pandemic wave (depending on the duration of immunity to the virus). The recommendation is that SARS-CoV-2 surveillance should be maintained until as late as 2024.
There has been a lot of confusion around COVID-19 testing and the landscape is evolving very fast. In this article, we want to make this information accessible to everyone. There are broadly two main types of COVID-19 tests:
- RT-PCR tests. They detect directly the presence of SARS-CoV-2 virus (or more specifically its RNA, the genomic instructions that the virus uses to invade and replicate inside our cells). These tests determine whether you are currently infected (even if you haven’t developed symptoms). It is considered the gold-standard for COVID-19 diagnosis by the WHO and has been widely validated in many laboratories across the world. They are commonly done from a nasopharyngeal swab.
- Antibody tests (a.k.a. serology tests). They assess if our bodies have acquired immunity against the virus, by detecting the presence of antibodies targeting SARS-CoV-2. These tests can tell whether you have been infected in the past, but they fail to detect whether you are currently infected (because it can take 1-3 weeks after infection to make antibodies). According to the CDC, “we do not know yet if having antibodies to the virus can protect someone from getting infected with the virus again, or how long that protection might last”. While RT-PCR tests have very high specificity and sensitivity, performance from antibody tests can vary significantly between providers. The main advantage over RT-PCR tests is that antibody tests generally have a lower turnaround time.
Another important aspect of this complex landscape is the regulatory status of a specific test. Regulation for in vitro diagnosis (IVD) can be quite difficult to navigate. Given the current situation of public health emergency, several countries are fast-tracking the approval of many IVD tests for COVID-19 testing.
For example, in the US the FDA is issuing Emergency Use Authorizations (EUA) for coronavirus-related medical devices (although is it important to mention that this is not equivalent to an FDA-cleared or FDA-approved device, since it is a temporary authorisation based on the current circumstances). FDA EUA requires, among other things, that the tests have been properly validated according to different criteria (including limit of detection, inclusivity, cross-reactivity and performance in clinical specimens). In the UK and the European Economic Area (EEA), IVD kits generally need to be CE marked (to indicate conformity with health, safety and environmental protection standards) and require approval by the relevant regulatory authorities (for instance, the MHRA in the UK).
Dr. Daniel E. Martin-Herranz is the CSO and co-founder at Chronomics