Although rates of COVID are still high in many places, access to free COVID testing is being dramatically scaled back. Here’s how to make the most of any tests you do have, to help protect those around you.
How is COVID testing changing?
As we move into the third year of the COVID-19 pandemic, access to free tests is changing.
In the UK, free lateral flow tests (LFTs, also known as rapid antigen tests or RATs) are no longer available in England, with exceptions for healthcare workers and people at high risk, with the other nations of the UK due to follow. We are also no longer able to offer PCR tests through the ZOE COVID Study.
A lack of federal funding for COVID measures means that widespread free testing may also come to an end in the US too.
Given that most of us will now have to buy our own COVID tests once we’ve run out of government stocks, we’ve been analyzing data from millions of health reports and test results submitted by our ZOE COVID Study contributors to figure out how to make the most of them as we move forward.
How effective are COVID home testing kits?
Our initial analysis of almost 100,000 test results reported in the ZOE app shows that home-based lateral flow tests (LFTs) are very good at detecting COVID-19.
We calculate test accuracy based on two measures:
Sensitivity: how well the test correctly identifies people with COVID - the more sensitive the test, the lower the chance of a false negative result (saying you don't have COVID when you do)
Specificity: how well the test correctly identifies people without COVID - the more specific the test, the lower the chance of a false positive result (saying you do have COVID when you don't)
This table shows the sensitivity and specificity of tests for the most recent variants, Delta and Omicron.
These results tell us that if you get a positive result on an LFT, you most likely have COVID. You also don’t need a PCR test to confirm it.
If you test negative, you probably don’t have COVID. However, it’s important to remember that around one in five LFTs will be a false negative result, saying you don’t have COVID when you actually do.
If you have symptoms that are highly consistent with COVID-19 but get a negative test result then it’s worth doing another one to confirm, if you can afford it. We also recommend avoiding socializing with others until you’re symptom-free to avoid passing on whatever illness you do have, even if it’s not COVID.
When should you test if you think you have COVID?
You should do an LFT on the first day you notice cold-like symptoms that might be COVID, such as a cough, runny nose, fever, headache or feeling very tired.
When rates of COVID are high, these symptoms are more likely to be caused by COVID than a cold, so you should do a test to be sure.
If you test positive, it’s recommended that you stay at home for at least five days, or until you feel well enough to carry on with your daily life.
However, our analysis shows that it takes an average of 8 days after the first positive test for people to report a negative test.
Interestingly, we also noticed a difference across age groups in how long it took for tests to turn negative again, with positive test results likely to persist longer in older people than in younger age groups.
Overall, our data suggest that it’s not worth doing another lateral flow test for at least 5 or 6 days after testing positive, as you’re very unlikely to test negative before then and you’ll just be wasting your kits. If you’re over 75, it’s worth waiting a bit longer.
If you test positive after this period, you should wait another day or two before you test again. If you test negative, it’s unlikely you’re still infectious but it’s a good idea to do another confirmatory test the next day, if you can spare it.
And, of course, please make sure you log all your symptoms and test results, whether negative or positive, in the ZOE COVID Study app, so we can continue to track the pandemic as official testing and monitoring is scaled back.
How to protect yourself and others from COVID
Although restrictions have lifted and testing is being scaled back, COVID is very much still with us.
The best way to protect yourself from becoming seriously ill with COVID-19 is to stay up to date with vaccines, getting them booked in as soon as you’re eligible.
The SARS-CoV-2 virus that causes COVID spreads through the air, so if you’re out in crowded or poorly ventilated places, you can protect yourself by wearing a well-fitting high grade face mask (such as an FFP2, FFP3, KN95 or N95) over your mouth and nose.
Finally, remember that as long as you test positive, you may still be infectious and can pass the virus on to people.
If you feel ill, whatever the cause, it’s best to stay at home, and wear a well-fitting mask if you do have to go out. Even if it’s not COVID, you won’t be spreading your germs to others who may be more vulnerable than you.
How you can help us keep track of COVID
It’s hard to predict what will happen over the coming months and years as we learn to live with the virus. But one thing we do know is that data is the key to understanding how COVID is continuing to evolve and spread.
Thanks to the millions of health reports, tests and vaccine doses logged by our contributors, the ZOE COVID Study has played a vital role in tracking COVID-19 symptoms and monitoring new variants as they emerge. Our ability to detect COVID based on these symptom reports and test results will become even more important as access to testing is reduced.
If you’re not already a Contributor, simply download the app and spend a minute or two logging how you’re feeling every day, as well as reporting the results of any COVID tests you take, whether positive or negative.
If you’ve opted in to our Wider Health Studies, you’ll also be contributing to groundbreaking research helping us to address some of our biggest health challenges, from cancer and heart disease to dementia and mental health.
Help science and keep logging.