We’re well into a second wave with thousands of new COVID-19 cases and escalating numbers of hospitalizations, use of intensive care beds, and deaths. We must work even harder to stop the spread of disease before our hospitals are incapacitated. But it’s challenging because one of the biggest problems with COVID-19 is that we are unknowingly infected and spreading the virus when we’re feeling healthy. We need to know if we’re infected before we have symptoms, and that means frequent and repeated testing for SARS-CoV-2 as a way out of the pandemic.
In short, the need for testing hasn’t changed, but the technology is finally catching up, and now we can test more people, more often.
Diagnostic Test Options for COVID-19
To diagnose an acute infection with SARS-CoV-2, we measure virus-specific genetic material (RNA) or proteins. An antibody test can be useful later because it measures a person’s immune reaction, but antibody levels are low or undetectable early on when the person is most contagious.
Newer tests using CRISPR gene-editing technology could be fast, cheap and user-friendly, but might take some time to get to the market. Other early warning testing options are also in development with artificial intelligence diagnosing asymptomatic COVID-19-positive people based on a cell phone recording of a forced cough and wearable technology that detects a high respiratory rate as an early sign.
So far, the ‘gold standard’ has been a SARS-CoV-2 PCR test, the most sensitive and accurate lab test, using the polymerase chain reaction (PCR) to detect viral RNA in even as little as a single molecule. It requires a nasopharyngeal (back of the nose and throat) swab and takes a few hours up to a couple of days for the results. It requires specialized labs, which makes them expensive, and because the PCR test is so sensitive, it might also register positive even when a person is no longer infectious.
The New Rapid Antigen Tests
However in am extremely promising recent development, protein tests have been used to detect SARS-CosV-2-specific antigenic viral proteins that provoke antibodies. They also use a nasopharyngeal swab but take only about 15 minutes to get a result. The test is also inexpensive as it is cheap to produce and requires trained professionals only to take the sample .
The tests are less sensitive because the sample must contain thousands of viral particles for a positive result and very early in the infection when there are only a few viruses, the rapid test might still be negative, which means missing infected people. Still, a positive rapid antigen test is accurate at the peak of infection in asymptomatic people, and within a week of the onset of symptoms when the number of virus particles is high.
In short, a rapid antigen test detects high-risk people who have had suspected exposure to COVID-19 or symptoms like a sudden loss of smell and taste, shortness of breath, or a high fever. But if the test is negative, then a PCR test is necessary, to be absolutely certain.
So although the rapid antigen test is not as sensitive, doing repeat tests in high-risk people might be as good or even better at catching infectious people and reducing the spread of SARS-CoV-2.
Getting a Rapid Test
Rapid antigen tests are now becoming available in Austria, but there is still some controversy about who will be administering them. The main plan is for people to make an appointment where the tests are available at special testing locations, pharmacies, clinical labs, or their doctor’s office, and have a trained person take the sample and do the test on the spot. The rapid antigen test is useful for screening people at airports, schools, universities, and potentially in the workplace.
The Future of Rapid Antigen Tests
The bottom line: A rapid antigen test is not as reliable as a laboratory test. But a cheap and simple test that might one day be available for home use would still be a game changer. A home COVID-19 test might be as simple as a home pregnancy test that provides a result within minutes and can be done daily.
There are challenges with self-administered tests – some people might not want to report their results or might be tempted get a stand-in to take the test for them to avoid quarantine or continue working. It’s also essential to educate the public about what the test results mean. For example, if there was any risk of exposure, then self-isolation is still necessary despite a negative test. A negative test could mean that there might not yet have been enough virus to detect and thus doesn’t give us permission to stop handwashing, mask-wearing, gathering in big groups, and social distancing.
But it gives us more information more quickly than we have had before. And that helps.