Scientists suggest that the test may be useful as part of a broader sorting strategy to slow the pace of the virus, which infected more than 7 million people and killed more than 250,000 people.
In a two-stage study, the sensitivity and specificity of the new test was studied at the stage of its development in the laboratory, and then on real biological samples of more than 300 infected patients.
The overall accuracy was 82%, with an overall sensitivity (how often the test correctly generates a positive result) of 57.6% and an overall specificity (how often the test correctly generates a negative result) of 99.5%.
In other words, the test was able to detect COVID-19 infections in about 6 out of 10 people, and it was almost perfect for determining the absence of infection. The test was more sensitive in patients with higher viral load, positively identifying the infection in about 7 out of 10 people.
The authors of the study say the test is faster, cheaper, and simpler, but not as sensitive as reverse transcription polymerase chain reaction (RT-PCR) tests that identify the virus based on its genetic material. It can be used to screen patients during peak periods of a pandemic. In the end, it can be useful in checking at-risk groups, such as health workers.
The COVID-19 Ag Respi-Strip® test was developed by the Belgian company Coris BioConcept, which specializes in rapid diagnostic kits for the detection of respiratory and gastrointestinal pathogens, such as viruses and bacteria.
The Coris BioConcept test is a type of immunochromatographic assay or sidestream test that detects the presence or absence of a specific substance. Most people may be familiar with another type of sidestream analysis – a pregnancy test.
In the case of COVID-19 Ag Respi-Strip, an antigen test uses a nasopharyngeal swab sample that looks like a long, flexible Q-tip that passes through one nostril and passes down the nasal passage close to the outside of the ear.
The antigen test works by looking for proteins on the surface of the virus. Coris BioConcept partially based the test on previous virological studies of SARS-CoV-1, which triggered the 2002-03 SARS epidemic. In fact, they are so similar that this COVID-19 e test can distinguish between SARS-CoV-1 and -2.
According to the authors, a 15-minute test for antigen, which can be performed in institutions where treatment is carried out according to several user-friendly protocols, can reduce the number of laboratory tests using RT-PCR by more than 13%.
They also note that the special material, reagents, and trained personnel needed to conduct molecular tests limit the number of analyzes that can be done quickly and on a scale, especially in poorer countries.
The main utility of the COVID-19 Ag Respi-Strip test will be in low- and middle-income countries where molecular analyzes are available in a very small number of laboratories, mainly only in capitals. However, they warn that COVID-19 Ag Respi-Strip is not intended for self-testing, but is used as part of testing by medical professionals.
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