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Vaccines are effective, but they will not be a sufficient form of protection against the next wave of infections. Still less than half of Poles are fully vaccinated. According to experts, this is not enough to talk about population immunity.

The spread of the virus is certainly limited by the now familiar DDM principle of distance, disinfection, and mask, as well as a system of testing symptomatic patients, tracking their contacts, and isolating the infected.

The gold standard for diagnosis continues to be molecular RT-PCR testing, which detects the genetic material of the SARS-CoV-2 virus and diagnoses ongoing infection. The test is performed in a diagnostic laboratory. For logistical reasons, the wait time for a result is as long as tens of hours. With mass population testing, this is also a large financial burden on the health care system.

A faster and cheaper alternative is antigen tests, which detect virus-specific proteins produced by multiplication. A result is available in as little as half an hour. As with RT-PCR tests, the material to be tested is taken from the nose or nasopharynx.

Until now, however, molecular tests have been thought to be more sensitive than antigenic tests.

Antigen versus molecular testing

British and Austrian researchers compared the effectiveness of two types of tests, molecular and antigenic, on the same group of primary care patients.

A study published in The Lancet suggests that antigen tests detect infection with high accuracy and may be an attractive alternative to RT-PCR tests. The prerequisite is that they are performed at the onset of infection and soon after the onset of symptoms.

In 1027 people with mild to moderate flu-like symptoms, both types of tests were performed to compare results. Many variables that may occur in real-world settings were taken into account: tests from five different manufacturers were used, analyses were performed in three laboratories, and swabs were collected in 20 general practitioners' offices.

In the molecular test, 826 patients were positive. Then the same group had an antigen test - 788 were positive. Only 38 antigen results did not confirm active infection.

The remaining 201 patients received a negative result on the molecular test, and 179 of them received the same result on the antigen test. False-positive results in the faster test were obtained by 22 diagnosed patients.

The authors then calculated the overall sensitivity and specificity of the antigen tests.

The sensitivity, or ability of the test to diagnose infection, was 95.4 percent. The specificity (the lower the percentage of false positives, the higher the specificity) of the analyzed tests reached 89.1 percent.

Comparable accuracy

- Our study highlights the need to test early in infection with antigen tests and shows that in patients who have early symptoms, both testing methods have similar levels of accuracy, said the publication’s co-author Jasmina Panovska-Griffiths, PhD, of the University of Oxford.

These results confirm previous reports obtained on much smaller groups of patients.

The sensitivity of the test depends on how the swab is collected.

Previous small studies have shown that if the swab was taken by an experienced clinician, it oscillated around 73 percent. If the patient swabbed by themselves, only assisted by medical staff, the sensitivity dropped to less than 56 percent.

Strategy for the next wave

The authors suggest that their findings may have implications for infection containment. Early and rapid detection of people with infection using reliable tests will better control the COVID-19 pandemic.

- Some countries are considering using antigen tests to manage future waves of pandemics, says Dr. Werner Leber of Queen Mary University of London.

Findings from the study suggest that implementation of antigen testing performed in primary care settings can facilitate immediate clinical decision making with high diagnostic confidence.

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And once the pandemic is over, how do we assess the impacts and losses? How do we develop a plan of action? The Periscope project brings together the best scientists and experts from 32 European universities, research institutes and think tanks. Gazeta Wyborcza is the only media outlet cooperating with them. The Periscope project is funded by the European Commission under the Horizon2020 programme.

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Translated by Chris Borowski

This is a translation of the article from July 29, 2021.

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