MedLife Raises the Alarm: Rapid Antigen Tests Not a Reliable Tool for Diagnosing SARS VOC 2 Infection Nearly Half of Rapid Test Results False Negative – Coronavirus

As a methodology, random samples were taken from people who attended the test on their own initiative, affirmatively asymptomatic or with mild and nonspecific symptoms. Oropharyngeal and nasopharyngeal exudate (from one nostril) was collected for RT-PCR and nasopharyngeal exudate was collected from the other nostril for antigen detection.

Manufacturer’s instructions on the transport and storage conditions of the biological product until the planned test for the harvested product in transport medium (VTM) 12 hours at a temperature between 2 and 80 C and 8 hours at room temperature, respectively 4 hours 2 to 80 C and 1 hour at room temperature if VTM transport medium is not used.

97 tests were carried out, 68 collected in VTM and 29 without VTM. Of the 68 samples collected in transport medium and kept at 2-80 C until testing, 38 were worked at an interval that exceeded the recommended 12 hours and 30 complied with the 12-hour interval, being worked at approximately 6 hours. hours after harvest. The remaining 29 samples collected without means of transport were processed within a maximum period of one hour from collection, keeping all samples at 2-80 ° C until testing. This was done taking into account the objective factors for conducting the virus identification tests, namely, field sampling and remote collection points from the performing laboratory.

For the 38 samples worked more than 12 hours after collection in VTM, of the 12 positive results by RT-PCR, 7 were also positive by the rapid antigen detection test. All negative results by RT-PCR were also negative for antigen detection. As a result, a sensitivity of 58% and a specificity of 100% were obtained for this sample.

Of the 30 samples worked within 12 hours after collection in VTM, of the 19 positive results by RT-PCR, 10 were also positive by the rapid antigen detection test. All negative results by RT-PCR were also negative for antigen detection. As a result, a sensitivity of 53% and a specificity of 100% were obtained for this sample.

Of the 29 tests performed on product collected without transport medium, of the 5 positive results by RT-PCR, 3 were also positive by the rapid antigen detection test. All negative results by RT-PCR were also negative for antigen detection. As a result, a sensitivity of 60% and a specificity of 100% were obtained for this sample.

For asymptomatic patients, the use of rapid tests is not recommended at this time.

In conclusion, the team that carried out the study points out that a sensitivity of 60% in real working conditions translates into the lack of identification of 40 SARS CoV-2 carriers out of 100 who will continue to spread the virus.

The average of the amplification cycles shows that the rapid test identifies only large viral loads (around cycle 22), not detecting those small viral loads that can be found both at the beginning and at the end, but without being able to distinguish between the two situations and without a threshold of amplification cycles beyond which there is no more contagion, ”said Dr. Roxana Vasilescu, GP of laboratory medicine, Head of MedLife Central Laboratory, coordinator of the study.

RT PCR remains the standard and tool used worldwide to identify carriers of the SARS CoV 2 virus.

The priority of the current pandemic is to detect and isolate those who are infected with the new coronavirus and, therefore, can transmit this virus to others. Due to its highly contagious capacity and the unpredictability of disease with significant and insufficient decompensations, early detection and multi-organ isolation, often lethal, of SARS CoV-2 carriers is essential to limit the spread of the disease and help to health systems to face the crisis. world.

For the identification of symptomatic but especially asymptomatic SARS carriers, the tests used must meet the following characteristics: be as sensitive as possible (to be able to identify the lowest possible concentrations of the virus, especially since, up to now, no known dose infectious), as precise as possible (correctly identify the presence of SARS CoV-2, taking into account that other viruses of the Coronaviridae family are already present worldwide; we are talking about the strains responsible for large volumes of tests and, finally , but not least, be cost-effective.In addition to these characteristics, these methods must be harmonized globally so that health policies and epidemiological monitoring are uniform.

“Until now, the RT-PCR method is considered the gold standard for the identification of viral RNA, being a method with convenient sensitivity and specificity to achieve the priority of the current pandemic. Although it is not a quick or cheap method and the realization of the necessary volumes is done with the serious involvement of human resources, it is still the standard and the tool used worldwide to identify virus carriers. In parallel, many laboratory test manufacturers are trying to develop a cheap and rapid alternative to the gold standard, namely the detection of viral antigens. Currently, many of these tests are being launched with better and better results. Unfortunately, however, no such test to replace RT-PCR has so far been identified to be introduced into policies and methodologies for surveillance and control of the new coronavirus infection anywhere in the world, “said the Dr. Roxana Vasilescu, general practitioner in laboratory medicine, Head of MedLife Central Laboratory.

According to the Order modifying and completing the Order of the Ministry of Health n. The legal framework for the use of SARS CoV-2 antigen detection tests has been created. Simultaneously with the rapid test, samples will be taken for RT-PCR. “Patients with a positive test result will be immediately isolated in Covid areas; patients with a negative rapid test result will remain in the buffer zone if they have symptoms that require hospitalization; If they do not require hospitalization, they will be left at home until the RT-PCR result is received. For asymptomatic patients, the use of rapid tests is not recommended at this time.