Are the new tests that detect covid-19 and the flu at the same time useful? -Coronavirus

Are the new tests that detect covid-19 and the flu at the same time useful? -Coronavirus

For nearly three years of the covid-19 pandemic, the antigenic tests carried out in particular in pharmacies have become familiar to our nostrils. This type of test has also been used, for even longer, to carry out influenza diagnoses. This winter, with the simultaneous waves of influenza and covid, several manufacturers (AAZ, Boiron, Toda Pharma, etc.) drew a new weapon, a combined antigen test, which makes it possible to know, for the same nasopharyngeal sample, which of the two diseases make us cough. And doctors and pharmacists began to offer them: “We started ordering these tests two months ago and, since then, we have performed an average of four or five a day”, explains Jean-Jacques Le Bian, boss of the pharmacy of the same name, in Guipavas (29).

On a French scale, demand is so great that one of the market leaders, the Ile-de-France laboratory AAZ, will find itself out of stock next week, its managing director, Fabien Larue, announced to Telegram. “Since December 15, we have pushed the production rate to 200,000 covid-flu tests each week”, he underlines, recalling that his product had been launched in the spring of 2022.

Are the new tests that detect covid-19 and the flu at the same time useful?  -Coronavirus
A nasopharyngeal influenza-covid antigen test has been offered by the AAZ lab since the spring of 2022 and demand exploded from the end of the year. (AAZ)

“A third of the flu is not detected”

What are these new tests worth in terms of effectiveness? “Independent studies have shown excellent sensitivity: out of ten influenzas and covid, nine are detected”, assures Fabien Larue. Solicited, “Bio Saiyan”, a well-followed medical biologist on Twitteris more nuanced: “We have a long experience of flu antigen tests. Their sensitivity varies depending on the year and the circulating strains, but it was possible to determine that on average, a third of influenzas were not detected”.

Imperfect, the combined antigen tests would still be of interest according to the biologist: “If they are used by a young person who has a fever, this allows him to make a flu diagnosis, and to isolate himself”. The leader of AAZ abounds: “In the event of a negative covid test alone, you do not isolate yourself. But if it shows that you are positive for the flu, you are not going to see your parents or grandparents”.

It would also be appropriate, according to Fabien Larue, to offer them to children in order to avoid wasting doses of antibiotics, in the midst of a shortage of pediatric amoxicillin. “We would thus reserve these doses for children who really suffer from bacterial infections and not from viral infections such as the flu or covid”. It is moreover for this specific indication that the High Authority for Health (HAS), recommended, in October 2020, the use of a “flu” antigenic test, as part of its latest opinion on tests allowing to differentiate covid-19 from winter respiratory infections.

This opinion also mentions the place of RT-PCR tests, carried out in the laboratory, which also exist for influenza. And they are incredibly reliable. Rather in line with the conclusions of the HAS, Bio Saiyan would advise them to patients at risk – pregnant women, people with heart failure or the elderly – for whom “we cannot be satisfied with tests as imperfect as antigens”. In the event of a positive PCR test, isolation, monitoring by the doctor, or even a prescription of Tamiflu, a drug against the flu, could follow for these patients, suggests the biologist.

A balance to be paid at the pharmacy

There remains the problem of reimbursement for these flu and covid tests. For antigenics made in pharmacies, a few euros are requested from the patient unless the pharmacist chooses to pay for them. For people who want to carry out a flu RT-PCR in the analysis laboratory, in addition to that of covid, a prescription from a doctor will not be sufficient for reimbursement by Medicare. “For this, you have to be a patient in an nursing home or hospitalized”, specifies Bio Saiyan, who pleads to redefine the strategy of flu tests by drawing inspiration from that used against covid-19.

A reassessment of the doctrine concerning flu and covid tests is well underway, confirms the HAS, seized for this, by the General Directorate of Health. But this evaluation of performance and usefulness relates only to antigenic tests. More specifically, the HAS will decide on the interest of using two categories of tests in children and adults: the combined covid-influenza tests and the covid-influenza-bronchiolitis tests that the AAZ lab has just completed. elsewhere to market. The opinion of the health authority, which can lead to a full refund, is expected, according to Fabien Larue, for the end of the month.

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