Will rapid testing be used by schools? It’s a question of balancing speed against accuracy
AREVIEW group, will report shortly on whether schools should be allowed to use quick turnaround antigen tests to detect if a teacher or pupil is positive for coronavirus.
Education Minister Norma Foley yesterday said no such recommendation has yet been made. But if they get the go-ahead, it means schools would no longer be entirely reliant on PCR (polymerase chain reaction) tests, which are the gold standard.
Antigen tests are already in place in some settings – along with PCR tests – such as hospitals and are used by the National Ambulance Service.
However, a debate continues on how they should be employed.
Current PCR testing
The current PCR test involves taking a swab sample from the nose or throat which must be sent to a lab for analysis. It is regarded as very accurate.
A nasal swab is also taken for an antigen test, with the result, in some cases, available within half an hour.
The question is how accurate they are.
They can detect only high viral loads, so it is possible that they may miss many people with lower levels of the virus.
However, they have many advocates here who say they should be used more widely across workplaces, in particular, to try to identify some contagious people who could otherwise unknowingly pass on the virus.
Use in schools
If they are used in schools, they would most likely be applied to contacts of a pupil or teacher who tests positive. Although they could pick up cases, the test would also miss some infections.
The World Health Organisation (WHO) stated that accuracy of these tests depends on factors, including the time from onset of infection, the concentration of virus in the specimen and the quality and processing of the specimen from a person.
These antigen tests have a role identifying positive cases among close contacts of a person who has been found to have the virus. If someone tests positive after an antigen
test, they must self-isolate. In cases where the result is “not detected” and there is a high index of suspicion they might have the virus, the guidelines say to carry out a PCR test.
These tests may be useful in speeding up the investigation of outbreaks.
Serial testing
Some teaching unions have proposed that antigen tests be used as part of surveillance
Serial testing with PCR tests is already in place in nursing homes, meat plants and direct provision. It means people are tested en masse every week or two weeks.
The idea is to be proactive and pick up cases which people are not aware of.
The WHO does not recommend use of antigen tests as a means of surveillance. The British Medical Journal said the tests have been used among asymptomatic people in realworld settings. The reported performance has been lower.
In a pilot study conducted in Liverpool, 60pc of infected asymptomatic people went undetected, including 33pc of those with high viral loads.
It said that, up to January 21, almost 560,000 tests had been carried out on more than 200,000 Liverpool residents, identifying 4,421 people who may not have known they were likely to be infectious.
Among students undergoing tests at University of Birmingham in December, only 3pc of those who would have tested positive on PCR were detected. Any use of tests in schools need guidelines.