Covid-19: 6 facts about France’s rapid antigen tests

France is set to roll out new rapid antigen Covid-19 tests as part of a new testing strategy in the coming weeks.

French President Emmanuel Macron made the announcement on Wednesday (October 14) during a live television interview, in which he also announced curfew measures.

Health minister Olivier Véran announced further details on the tests the following day.

Here is a rundown of what we know so far.

PCR, antigen, serology...what’s the difference?

There are three types of tests available for Covid-19, molecular (PCR), antigen and antibody (serology). The first two detect whether a person is currently infected with the virus, the serology detects if a person has had the virus in the past.

Molecular tests look for evidence of SARS-CoV-2, the virus that causes COVID-19, in the nose, throat, or other areas in the respiratory tract.

Antigen tests look for evidence of proteins that make up the SARSCoV-2 virus.

The antigen tests can provide results in under one hour, while the PCR tests often take at least a day, sometimes up to one week.

France has ordered 5 million antigen tests

France has ordered five million doses of these antigenic tests recognised by the World Health Organisation and the Haute Autorité de Santé.

"They have been in use for several days in all French regions," Mr Véran said, adding that "experiments are still being conducted".

They will not be available immediately

Despite the optimism of the government these new tests are not yet ready. It will be necessary to "equip" pharmacies and practitioners”, Mr Véran said.

The health minister has acknowledged that it will then be necessary to wait for "the opinion of the scientific authorities" before "envisaging a widespread deployment in the coming weeks".

They allow for fast results

This is the great advantage of these tests. The results should not take several days, as is the case with PCR tests.

Mr Véran has said he expects them to deliver results in "between 10 and 30 minutes, depending on the tests".

Mr Macron was also enthusiastic about these tests: "It changes a lot. We will be able to do them in pharmacies, at different points. So we'll have more points of support, not just in laboratories".

They are less reliable than PCR tests

Rapid antigen tests are less sensitive than other testing methods currently used in France, which is one of the main reasons that their use is recommended only on symptomatic patients.

Antigen tests are useful for “detecting infected subjects with a high viral load”, meaning the most contagious subjects, the public health body Assistance Publique-Hôpitaux de Paris (APHP) wrote in an evaluation published on October 1.

Virologist Yves Gaudin told newspaper the Parisien: “When we do a PCR test, we amplify the viral genome. So we can detect it as soon as there is just a little bit of it.

“A rapid antigen test involves the detection of viral proteins, but without an amplification phase. If there are only a few at the start, we will have a very weak signal and risk missing the infection. As a result, the proportion of false negatives is likely to be higher,” he said.

The APHP said that a positive result should be confirmed by a PCR test.

The could be used principally at airports

The APHP stated that "the generally satisfactory performance of certain antigen tests makes them a tool of choice for carrying out mass testing in low-prevalence populations (airports on arrival, universities, companies, local authorities, etc.), which today escape PCR testing or unnecessarily clog up medical biology laboratories".

Prime Minister Jean Castex also said: "Airports are really going to be among the priorities for the rapid deployment of antigenic tests".

Read more about coronavirus testing:

France to release five million 30-minute Covid-19 tests

'Fast, cheap, painless': Covid saliva test from French lab

Covid-19 France: Is less testing a good thing?