COVID tests - PCR vs lateral flow
PCR tests (polymerase chain reaction tests) were used since the start of the pandemic to test for the presence of the virus, and they can be used to alert scientists to any new variants circulating.
A PCR test needs to be ordered from the government website or taken at a local test site. It's sent off to a lab, and results can take one to three days to return.
Lateral flow tests came in a bit later in the pandemic, and can be done at home, with the result available 20 to 30 minutes later. They were initially regarded as inaccurate, but are now regarded as highly accurate at finding a positive result for those infected.
Deciding which is best depends on whether you have symptoms or not. When to isolate with symptoms depends on whether you are vaccinated or not.
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Using a lateral flow test with no symptoms
Lateral flow tests are a very reliable way of testing those without symptoms. When COVID-19 rates are high in your area, it’s a good idea to take a lateral flow test before you meet family or friends outside your household, or before events with lots of people. If you go to work or your children go to school, it’s a good idea to take these periodically, perhaps once or twice per week.
Lateral flow tests can be used if you are fully vaccinated (or under 18) and have had close contact with someone who is positive. You do not need to self-isolate but you should take daily lateral flow tests for 7 days.
If at any point, it becomes positive, you must begin your self-isolation.
Using a lateral flow test to end self-isolation
If you have a positive lateral flow test and no symptoms, you no longer need to confirm this with a PCR test, and self-isolation begins the day of your positive result. If you are fully vaccinated, self-isolation can end after 5 full days, as long as you have negative lateral flow tests on two consecutive days, ie Day 5 and Day 6.
If you continue to have a temperature or you're still getting positive results, you must wait for two negative results two days running, or up to the end of Day 10.
When should I get a PCR test?
A PCR test should be ordered if you experience COVID-19 symptoms, and you should self-isolate in your home until you have the result.
Symptoms were classically a fever, cough and change to your sense of taste or smell. However, if you are fully vaccinated, and with new variants like Omicron circulating, symptoms may also include a sore throat, sneezing, a runny nose, headache or fatigue.
If your PCR test comes back positive you must continue to self-isolate according to government guidelines. If your PCR test is negative, you may end your self-isolation.
If you experience symptoms, you should self-isolate immediately and order a PCR test. In the meantime, you can take daily lateral flow tests. If a lateral flow test comes back positive at any time, then you can cancel your PCR test as you do not need a confirmatory PCR test, and begin your self-isolation.
To help the NHS Test and Trace app, it is helpful to get a PCR test done as quickly as possible, whether this is positive or negative does not affect your self-isolation. It does help to identify other positive contacts and inform on new variants in the community.
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