Self-collected nasal swabs may be a reliable alternative to nasopharyngeal swabs

Under certain conditions antigen Testing with a cotton swab self-collected from the anterior nose may be a reliable alternative to antigen testing with a nasopharyngeal swab collected by a healthcare professional.

This is a conclusion drawn by a team of Charite researchers (Universitätsmedizin Berlin and Heidelberg University Hospital). The results of their research are European Respiratory Journal..

Rapid antigen testing may be less reliable than PCR testing, but its speed and simplicity are important because it can help control current pandemics and reduce risk in certain everyday situations. It is a complementary tool.

Rapid antigen testing is intended for use at the Point of Care. If you check if a person is infected and infected during the test, you can get results within 30 minutes. Therefore, this type of test can be used to allow people to visit their loved ones more safely in care facilities and hospitals. Despite this possibility, they are not yet widely used.

One reason for this is that, in the past, most antigen testing systems have used nasopharyngeal swabs that require collection by trained medical staff.

“There are two reasons why expert-collected nasopharyngeal swabs are a barrier to the spread of rapid antigen testing,” said Dr. Frank Mockenhaupt, deputy director of the Institute for Tropical Medicine and International Health at Charité. ..

“First, most people Nasopharyngeal swab It is unpleasant and may avoid regular testing. Second, swabs constrain staff resources, are complex, time consuming, and require the use of personal protective equipment. “

Therefore, in collaboration with PD, Professor Mockenhaupt, head of the clinical tropical medicine section of Heidelberg University Hospital, said that a self-collecting prenasal swab administered under medical guidance would replace the expert-collected nasopharynx. Designed a study to test if we can provide a cotton swab.

The study, conducted at Charite’s outpatient coronavirus testing facility, was conducted from late September to mid-October. Individuals with characteristic SARS-CoV-2 symptoms who wish to participate in the study were instructed by medical staff on the procedure for self-collected nasal swabs.

Participants were instructed to insert a swab into both nostrils to a depth of 2-3 cm and rotate it against the nasal wall for 15 seconds. This was followed by expertly collected nasopharyngeal swabs. Both swab samples were analyzed in the field using a commercially available rapid antigen test approved for use in Germany.

Then we compared the test results. Staff also collected nasal pharyngeal (nose and throat combination) swabs and analyzed them using PCR tests. It served as a diagnostic reference standard.

Based on the PCR results, 39 (13.5 percent) of the 289 participants were diagnosed with SARS-CoV-2. In 31 of these infected individuals (about 80%), expert-collected nasopharyngeal swabs also tested positive for rapid antigen testing.

In the case of self-collecting swabs collected from the anterior nose, 29 (about 74%) of infected individuals gave correct results.

“Of course, I expected rapid antigen testing to be less sensitive than PCR,” said PD Dr. Denkinger. “However, upon closer examination, cases of antigen testing with no evidence of infection were primarily associated with patients with low viral load.”

When examining only virally loaded patients, researchers found that antigen testing correctly identified all positive samples obtained via nearly 96% of nasopharyngeal and self-collecting swabs. did.

“This study shows that monitored self-administered swabs are as effective as expert-collected nasopharyngeal swabs when used in combination with the antigen tests selected for this study,” PD said. Dr.

She adds: “A cotton swab that is more suitable for use on the front of the nose may further improve the accuracy of the test.” In November, the federal government swabmed, including by trained staff in nurseries and schools. Introduced legal provisions that pave the way for the wider use of antigen testing.

“The new legal provisions have eliminated the reliance on medical staff,” said PD Dr. Denkinger. “This makes rapid antigen testing more suitable for large-scale deployments. Research data on self-collecting swabs, such as the findings from this study, will help those responsible for discovering and implementing new concepts. . “

Rapid antigen testing is an important additional resource to supplement our tense PCR-based testing capabilities. Not surprisingly, self-collecting swabs and self-management tests are not without problems. For example, tests that are misperformed or interpreted can provide false reassurance. On the other hand, the positive result of the rapid antigen test should always be confirmed by PCR. “

Dr. Frank Mockenhaupt, Professor, Deputy Director, Institute for International Health of Tropical Medicine, Charité-Universitätsmedizin Berlin

Therefore, as a next step, the research team wants to study whether rapid antigen testing produces reliable results, even when used by laymen without expert guidance or supervision.