MINISTER FOR EDUCATION Norma Foley has claimed that the use of rapid antigen tests in schools has not been recommended by the World Health Organisation (WHO).
Teachers’ unions have called for regular antigen testing to be introduced in schools as part of plans to re-open educational settings on a phased basis from next week.
However, Foley claimed in a radio interview this week that the WHO was not in favour of the measure.
The WHO’s guidance is complicated and contains a number of qualifications which supports the use of antigen tests in schools in some scenarios, but advises against it in others.
Therefore, this article will not provide any verdict on the minister’s claim, but will instead lay out the advice on where rapid testing is deemed appropriate in schools.
The Claim
The minister made the claim on RTÉ Radio 1′s News at One programme on Wednesday.
In a segment about the gradual re-opening of schools from next week, Foley was asked whether the use of antigen tests had been considered by the government.
Presenter Bryan Dobson highlighted that there have been ongoing calls by teachers’ unions to introduce so-called rapid testing, before suggesting that such a move could be “a very powerful weapon” to help keep schools open.
The minister said:
I appreciate the point you made there, but in the first instance I should have to say that the World Health Organisation does not recommend antigen testing in schools.
She added that there were “mixed views” about the efficacy of antigen testing, and that an expert group currently examining the use of such tests would make recommendations in the coming weeks.
Antigen tests
Firstly, let’s look at what an antigen test is and how it differs from the PCR tests that are more commonly used to detect Covid-19.
Like PCR tests, antigen tests use a swab to take a sample from the nose of a person who is suspected to have Covid-19. However, they generally do not take swabs from a person’s throat.
They are relatively inexpensive and can be used at the so-called point of care (in other words, people don’t need to travel to a centre to get swabbed).
Antigen tests are particularly useful because unlike PCR tests, the sample taken from a person during the testing process doesn’t need to go to a lab. That means that results arrive very quickly, typically between 15 minutes and half an hour.
The cost, ease-of-use and rapid turnaround time for results from antigen tests means that they are seen as having the potential to significantly expand countries’ testing regimes.
They also have the potential to help reduce case numbers by preventing delays in diagnosis.
The European Centre for Disease Control (ECDC) has said that antigen tests can help reduce the transmission of Covid-19 by enabling the early detection of cases and to help contact tracing to begin more rapidly.
They are already used in Ireland in a few cases too. According to the HSE, antigen tests are used in some hospital patients who show symptoms of Covid-19 and among others based in settings where a Covid-19 outbreak has occurred.
However, there are drawbacks. In her interview with RTÉ, Foley outlined concerns about the accuracy of antigen testing in detecting cases of Covid-19.
Although antigen tests can find virus samples in people who are sick with Covid-19, this doesn’t always happen.
That’s because test sensitivity is generally lower in antigen tests than in PCR tests, meaning that some positive cases will be missed – which could lead to further cases if a person who has Covid-19 mixes with others because they believe they are not sick.
Their performance is also likely to depend on when a person is tested: research suggests that antigen tests work only when the person being tested has a higher viral load (i.e. when more virus present in their body).
This usually happens in the pre-symptomatic phase (1-3 days before symptoms occur) and early symptomatic phases of Covid-19 (within the first 5-7 days of illness).
But because the official estimated range for Covid-19 is around 14 days, antigen tests may miss the phase when a person’s viral load is lower, particularly during the second half of that two-week period. That could lead to false negative results.
WHO interim guidance
However, the claim that we’re examining isn’t about the accuracy or performance of antigen tests; it’s about the situations in which the WHO advises that antigen tests could be used.
The UN agency is still gathering information in order to better understand how rapid testing could help in the fight against Covid-19, but it did publish interim guidance on the use of antigen tests last September.
Although it acknowledged that data on the overall use of rapid testing was limited, the WHO suggested that antigen tests “could play a significant role” in managing Covid-19 outbreaks by informing public health decision-making and surveillance of the virus.
One of the key recommendations within the guidance was that antigen tests, where used, should be able to identify 80% or more positive cases correctly and have at least 97% specificity (meaning that 97% of tests give a true result).
Crucially, the advice also lays out a number of scenarios and locations where the use of antigen tests could be appropriate if the kits used were to meet these requirements.
These include scenarios where PCR testing is unavailable, or where a quick turnaround time for test results is required by health officials.
And the guidance names two situations where antigen tests could actually be used in schools.
One is to support investigations of clusters where outbreaks have already been confirmed in ‘closed’ or ‘semi-closed’ settings – such as schools, care-homes, cruise ships, prisons, or workplaces – with PCR-type tests.
“AgRDTs [antigen tests] could be used to screen at-risk individuals and rapidly isolate positive cases (and initiate other contact tracing efforts) and prioritise sample collection from RDT-negative individuals for NAAT [PCR-type tests],” the advice reads.
In this scenario, antigen testing could be used in a setting where Covid-19 has already been confirmed through PCR testing, to find out whether the virus has spread to a large number of close contacts.
Teachers’ unions
But that part of the guidance outlines a reactive approach, which recommends the use of antigen tests in response to an outbreak that has already occurred.
Some teachers’ unions have instead sought a more proactive approach: they have pushed for the introduction of serial testing for potentially asymptomatic members of school staff, to prevent outbreaks before they occur.
At the start of February, Fórsa pressed for “enhanced access to serial antigen testing for SNAs and other school staff”. Earlier this week, the Irish National Teachers’ Organisation (INTO) also said it had sought the introduction of “regular antigen testing”.
Regular or ‘serial’ testing for Covid-19 - using PCR tests – has occurred in other workplaces in Ireland during the pandemic.
Last year, the government introduced ongoing serial testing in nursing homes in response to high numbers of cases and the high vulnerability of older sections of the population to the more adverse effects of Covid-19.
Serial testing also took place at food-processing facilities, including meat plants, due to (among other things) the congregated nature of work in factories and the lifestyles of workers (who often shared accommodation and transport to and from work).
And serial testing was not just limited to workplaces: it was also introduced in Direct Provision centres – residential settings where people live in clusters – last autumn.
It is worth pointing out that in all of these settings, serial testing was introduced reactively, after large clusters often involving dozens of cases occurred in nursing homes, meat plants and Direct Provision centres.
Although a number of outbreaks have been linked to schools since they returned last August, none of these are currently active (because most schools have been closed since before Christmas), meaning that a decision to introduce serial testing would now be proactive.
Asymptomatic cases
One interpretation of the WHO’s advice does suggest that antigen testing could be used to prevent large outbreaks from occurring ahead of time.
Part of the agency’s guidance states that in a situation where there is widespread community transmission of Covid-19, antigen tests could be used “for early detection and isolation of positive cases” in places like care homes, prisons, and schools.
The advice does warn that those who produce a negative result with an antigen test should be managed safely, and that the result “cannot completely exclude an active Covid-19 infection”.
It therefore suggests that if rapid testing occurs in this scenario, there should be repeat testing where possible along with the continued use of PCR-type tests to confirm cases, particularly among patients who show symptoms of Covid-19.
However, there is a catch; the advice later suggests this should also occur when the ability of health services to carry out regular PCR testing is diminished.
It suggests that if this were to occur, antigen testing could be used if it was not possible to test all or any suspect cases of Covid-19 using PCR-type tests.
But the WHO also outlines a number of situations in which antigen tests should specifically not be used – including settings such as screening at points of entry at airports, for blood donation, and elective surgery.
Crucially, another scenario deemed inappropriate for antigen testing is in “individuals without symptoms unless the person is a contact of a confirmed case” of Covid-19.
The WHO suggests that where a person does not have symptoms of Covid-19 and has not been in contact with a confirmed case, the likelihood that they have Covid-19 – based on epidemiology, case contact, and clinical findings – is low.
Asked by TheJournal.ie to clarify her remarks following her claim on News at One on Wednesday, a spokesperson for the Minister pointed to this part of the WHO’s advice.
“The current WHO advice on antigen testing is that it is “reasonable to use to investigate outbreaks”. However, it is also advised that Ag-RDTs should not be used in routine surveillance testing where there are zero or only sporadic cases,” a statement said.
‘Widespread community transmission’
This is where things get complicated.
On the one hand, the WHO specifically does recommend the use of antigen tests in schools in some situations.
Its advice can be interpreted as supporting regular testing where there is widespread community transmission of Covid-19 to detect cases early and to isolate those who test positive.
But this recommendation appears to be dependent on situations where PCR-type testing is no longer available because the testing system has become overburdened.
Furthermore, the phrase ‘widespread community transmission’ remains somewhat open to interpretation.
Community transmission is when there is no clear source of origin of the infection in a new community, but there is no specific threshold for what constitutes when this is ‘widespread’.
During Ireland’s second wave in October, health officials believed there was widespread community transmission before recommending six weeks of Level 5 restrictions – on Monday 12 October, Dr Tony Holohan specifically said as much.
On that date, 825 new cases of Covid-19 were confirmed and the 14-day incidence was 168 per 100,000 people.
The national incidence is now well above 200 per 100,000 people, but there were fewer new cases announced every day this week than on 12 October, and Professor Philip Nolan said at a briefing of NPHET on Thursday that community transmission is now falling.
There is also issues around where the ‘community’ being referred to is: in Ireland, there could be widespread community transmission in a certain county, or certain parts of a certain county, while other parts of the country remain free from new community cases.
Even where it’s agreed that there’s widespread community transmission, the WHO says rapid testing would not be appropriate in people who are not symptomatic or deemed close contacts – which would appear to rule out regular rapid testing in schools.
Analysis
The WHO’s guidance does recommend the use of antigen tests in schools under a number of scenarios.
It allows for antigen testing in schools if health officials are seeking to find new cases of Covid-19 among close contacts in settings where a small number have already been confirmed.
Another possibility is where there is widespread community transmission and the health system has become so overburdened to the point that PCR-type testing is no longer possible for all potential cases.
This happened in Ireland as recently as January, when a massive spike in new cases forced the health service to stop testing those deemed close contacts of confirmed cases.
If schools were open in that scenario, the WHO’s advice would allow for antigen testing to find new cases and prevent clusters.
But the current guidance also appears to rule out serial antigen testing in schools, which is what teachers’ unions have called for.
Such a measure would involve testing, on a regular basis, thousands of asymptomatic people who would not be deemed close contacts of confirmed cases, which the WHO specifically says should not happen.
The minister’s spokesperson also referenced that part of the advice when clarity was sought on her claim.
The WHO’s advice, though saying antigen testing can be used in some scenarios, is heavily qualified and does not mention serial testing.
The situation in Ireland may become clearer in the coming weeks.
An expert group is currently looking at the issue of antigen testing in asymptomatic groups for NPHET, and a report on their use is expected in the coming weeks.
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