How Accurate Are COVID Home Tests?
One of the most important tools in the fight against COVID has been testing, which emerged very early on in the pandemic. Although the US is now experiencing a drop in Omicron cases, testing remains a crucial part of containing the virus and minimizing risk.
Now, testing has advanced to the point where individuals can test themselves at home, without the time or expense of visiting a medical office or waiting for results to come back from a lab. Rapid testing has offered an added layer of protection in helping countries monitor the spread of the virus and take measures to keep people safe. At-home tests were difficult to find at first, but are now more widely and readily available. This means people can more easily test themselves in the comfort of their homes and have their results within 15 to 30 minutes.
However, at-home tests and laboratory tests for COVID use different methods. The historic “gold-standard of Lab tests are PCRs – also known as polymerase chain reaction tests, – and focus on the molecular structure of the virus., while the at-home versions (“lateral-flow antigen tests) test for the antigens that the body produces in response to the virus. These lateral-flow antigen tests use decades-old technology. What’s more, there are questions about whether the at-home tests are accurate.
There are a number of reasons for this, including the lower sensitivity of the antigen tests as well as human error. As a result, the Washington Post reported, a number of people have experienced false negative results from an antigen test but later tested positive in a PCR.
How accurate is home testing?
PCR remains the gold standard when it comes to COVID testing. Studies have consistently shown that the PCR test technology is considerably more accurate than the at-home antigen versions. This is because the PCR test amplifies the presence of the virus by replicating it, which makes it easier to determine if the virus is present. According to research by the Center for Health Security, PCR tests produce higher sensitivity and specificity compared to antigen tests.
However, the home antigen tests are certainly useful, if you keep their limitations in mind and use them as intended – with frequency and consistency over time, in advance of gathering with others. Because of the limitations of the lateral-flow technology used to identify the presence of antigens, the tests aren’t always able to pick up the virus in its earliest stages. This means there’s a greater risk of getting a false negative as well as a false-positive result. False-negative results are a more significant problem. For example, when you go out to a business event, or visit with immune-compromised friends or family members when you think you are negative but instead are positive and end up impacting office productivity, or worse getting vulnerable people seriously ill.
The best at-home tests say they are about 85% accurate but in the real world, the data comes in at considerably less impressive numbers of 50-%-70% at best, which means that 30% of people who actually do have the virus get an inaccurate picture of their health and transmissibility with these tests. But the tests are significantly more accurate in people who are at the height of transmissibility.
Other than the difference in the testing methods, antigen tests are also more likely to be administered by someone who doesn’t have medical training, or who isn’t carefully following the results – thus further degrading results. A study by Nature in June of 2021 pegged the Abbott BinaxNow test as only 35% accurate in asymptomatic individuals. There’s a set procedure that people need to follow for the test to be accurate, and the tests from some manufacturers may have directions that are easier to follow than others.
Issues with the reliability of antigen testing have led to some facilities halting rapid on-site testing. For example, the state of Utah recently halted all antigen testing. This was done after it emerged that there were “higher than expected” numbers of false negatives on antigen tests in comparison to PCR test results.
The future of COVID testing?
Reliability issue notwithstanding, antigen testing remains a vital piece of the puzzle when it comes to reducing the spread of COVID-19. There is now new microfluidics testing technology available that greatly increases the accuracy of results far beyond the reach of lateral-flow home testing – to 97.6% in symptomatic individuals and 84% in asymptomatic individuals. These new technology manufacturers are anticipating further increases in speed (to a ~5-min test run-time) and sensitivity (already almost as accurate as PCR and soon to be even more so). These tests are available at mobile CLIA labs in the Boston area from providers like AllClear Healthcare. What’s more, the benefits of these state-recorded, highly accurate, rapid turnaround tests will help make for safer corporate events, travel, and visits to family and friends should new variants emerge. Improving accessibility will make it more likely that people will take these tests, and that’s to everyone’s benefit.
However, as the virus mutates, testing manufacturers will continue to need to keep up with the changing nature of the virus with advances in testing technology beyond the underperforming lateral-flow technology that is currently under-serving the public health mission for our communities.
As we can see, as COVID-19 evolves, COVID testing needs to constantly be evolving to adapt and better support the public health mission. With the development of more accurate testing options, we might finally be in a position to drive cases down for good.