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Pros and cons of rapid antigen tests

A rapid antigen Covid-19 test (File photograph)

Rapid antigen tests to be used by airline passengers from Bermuda to destinations except Boston and Canada are cheaper and faster than the usual PCR tests, researchers have said.

But they added antigen tests were also less accurate than the “gold standard” PCR method and produced some false positives.

The health ministry announced last Sunday that antigen tests would be allowed for airline passengers travelling to all destinations except Boston and Canada - which do not accept the tests for arrivals.

The ministry said earlier it would allow the importation of antigen tests for personal use.

But officials highlighted there were many fake antigen tests on the market and that the Department of Health and Customs would check consignments to make sure they were authentic.

Officials added that antigen tests were a rapid screening tool and that a positive result should be followed up immediately with a test by PCR.

A ministry spokeswoman said: “It is hoped that the public can use antigen kits for personal use to empower themselves - whether vaccinated or not - to protect vulnerable persons in their midst, for example, before visiting an elderly relative or before attending a social gathering with loved ones.”

Results from antigen tests can also vary depending on what brand of test is used.

It is not yet known what tests Bermuda will use but details on the policy change are expected to be announced later this week.

An article on the website of the Cleveland Clinic, a leading US hospital, said antigen tests could be taken at home or by a medical practitioner with a result in about 20 minutes.

The article said the tests looked for antigens - proteins produced by the virus that sparked a response by the body’s immune system, similar to tests for strep throats.

The widely used Ellume antigen test does not require a prescription and has been cleared for use by symptomatic and asymptomatic people.

Anyone aged two and up can have the test.

The test has its own smartphone app that gives a walk-through on how to collect a specimen with the included swab.

The device tests the specimen and delivers results in about 15 minutes to the app through a bluetooth connection.

The at-home tests are affordable and keep potentially infected patients at home.

But the quality of collected specimens can vary because they are being administered by a user and not a medical provider and an incorrectly-collected sample can lead to an wrong test result.

Antigen tests are also slightly less accurate than PCR tests, and can generate false positive results in asymptomatic people.

Gary Procop, an infectious diseases expert at the Cleveland Clinic, said: “If a person is asymptomatic but has been exposed to someone else who has Covid-19, it can create some confusion as to whether it’s a false positive or an accurately positive test.”

He added that, if that was the case, extra testing would be required.