Antigen testing, for so long the poor relation in finding out if someone has Covid-19, has been dramatically brought in from the cold. For much of the year they were looked at with suspicion by senior public health doctors.
They even turned up in a “snake oil” reference. But the DIY tests, which offer a quick result, are now to become part of the everyday tool kit to help us work, socialise and be entertained in the coming weeks and months.
Rapid versus gold standard
PCR tests are still regarded as the gold standard in Covid-19 testing. They are highly accurate but they are costly and must be sent to a laboratory for analysis.
A rapid antigen test can be done at home with a self-swab or professionally and provides a result in around 15 to 30 minutes.
Instruction is recommended and YouTube videos are online. They are not as accurate, but if done when a person is most infectious they could be around 80pc reliable, according to some studies. They perform best in symptomatic people around three to five days after exposure to the virus.
Story so far
Ireland has not embraced their use as enthusiastically as other countries. Chief medical officer Dr Tony Holohan has been cautious about rapid antigen tests offering false reassurance and there has been good access here to PCR tests.
The antigen tests have been used in some hospital outbreaks. Private employers, including in food processing, have also invested in them in an attempt to reduce the chances of a worker coming in positive and infecting others. The HSE has just finished a four-week pilot involving their use in a number of nursing homes.
Pilots have also been carried out in childcare facilities and third-level colleges. Generally the person takes a test twice a week at home or on site and reports the results online to the HSE. The findings are now being analysed by the HSE to see whether they can be made a permanent feature.
Anyone who tests positive on an antigen test should self-isolate and is referred for a PCR test.
In the past four weeks, almost eight in 10 of the 10,248 members of the public who came up positive in an antigen test also turned out to have the virus when they had a PCR test from the HSE.
The National Public Health Emergency Team has for the first time signalled it sees a role for rapid antigen tests as part of a wider package of safeguards.
It will look for more guidance from the expert group chaired by Professor Mary Horgan. One of the areas they will be used in is in the testing of fully vaccinated people with no symptoms who are close contacts of a confirmed case. They stopped being tested last month.
But, under the new plan, they will be sent free antigen tests to their home by the HSE. They will get guidance and could be told to take a test on four different days, although the HSE said yesterday it had not yet finalised the details.
People are likely to be instructed online on how to use them. There will also be an effort to see whether people who cannot get fully vaccinated because of a medical condition might be able to incorporate them in their Covid-19 pass.
Their wider use in indoor events has yet to be clarified. Immunology expert Professor Kingston Mills of Trinity College Dublin said his opinion was that they could be used in schools. A pupil would get the test at home twice a week. If they are positive they would then stay at home.
With the reopening of nightclubs and other entertainment venues, people attending will be encouraged to take a test on the day.
It is not yet clear how they could be used in a bigger scale for events such as concerts.
Antigen tests are now widely available in shops and pharmacies. Prices vary but one test could cost around €8 and a pack of three €20.