What you need to know about rapid COVID test kits

The emergence of the omicron variant is sparking a scramble for COVID lateral flow tests, to try to ensure safe Christmas parties and family gatherings. The UK is grappling with a supply shortage of these faster and cheaper tests, known in the US as rapid tests, after health officials said last week that they are as effective at detecting the omicron variant as they are for the delta. which until now was the most contagious.

In the United States, President Joe Biden said he will deliver 500 million free COVID-19 tests to people in their homes starting next month and that he will send the Army to help in overwhelmed hospitals in the face of the new wave of viruses it faces. U.S.

When Should You Get Tested After Possible COVID-19 Exposure?

The best time to test is two to three days after exposure to someone who has the virus, according to Irene Petersen, a professor of epidemiology at University College London. This is because the moment in which people begin to infect is variable. If you sat next to someone who had the virus on Friday, you should get tested on Monday.

I’m going to attend a Christmas celebration. When should I get tested?

Just before leaving his house, Petersen said. Do not trust a negative test from two days ago, “it could have been infected in that time”.

Can I trust the result of a negative lateral flow test?

Don’t trust a test done a few days after exposure, Petersen noted. You should continue to be tested for about a week after exposure to the virus.

His test came back positive. Now what?

To begin with, it is best to rely on the quick test.

“You most likely have COVID if your lateral flow test came back positive,” Petersen said. There is reportedly less than one false positive for every 1,000 lateral flow tests performed.

The official indication in the UK is that after a rapid test positive, you should have a PCR test and self-isolate until the result is confirmed. If a PCR performed up to two days after a rapid test is positive, a 10-day isolation should begin. If a PCR is performed after that, regardless of the result, it should still be isolated for 10 days.

Petersen advises people to stay home immediately after testing positive for a rapid test, especially if they start to have symptoms. “If you have a fever or runny nose and a positive lateral flow test, you are infected,” he said.

What is the difference between rapid tests and PCR?

A lateral flow test investigates whether a person has proteins from the virus in their body. A person is more likely to have a high level of these proteins when they are most contagious, so they may be less accurate just after being infected or towards the end of their illness. It is also known as a rapid test because it can be done at home and gives results in as little as 15 minutes.

A PCR test, which identifies the genetic material of the virus, must be verified and interpreted by a laboratory. Delivery of results can take up to two days and is more expensive than the lateral flow test.

PCRs are more sensitive in detecting the virus, since the genetic material that may be in the samples is amplified in the laboratory. That means it can detect disease earlier than the rapid test. A PCR can detect the virus from day two to 16 days after infection, according to the Robert Koch Institute.

With a PCR, a person can test positive even if they are no longer infected, as they may still have some genetic material from the virus, Petersen said.