Principle of operation of POC Antigenic Tests
The antigen test detects viral proteins. These so-called "rapid antigen tests" reveal patients at the peak of the infection, when the body has the highest concentration of these proteins. It is as such that the highest risk of transmitting the infection to other people. Compared to RT-PCR tests, the advantage is lower demands on the expertise of medical staff in sampling, the possibility of evaluating the test directly on the site and the speed of this evaluation (time from sampling to the result does not exceed 30 minutes) and it is 10 times cheaper. On the contrary, the disadvantage is that they are not as sensitive as the standard RT-PCR tests used to accurately identify those infected according to the algorithm of the Ministry of Health.
They identify you upon arrival, have an OP or CP with you. You will receive an e-Request, it will take up to 3-5 minutes for the healthcare professional to handle this administration. The collection will take approx. 1-2 min. for the test taker, the collection itself is the same as for PCR tests, i.e. swab the nasal cavity with a special stick. Execution, evaluation and registration of the test result take 15 - 35 minutes. In total, the test taker waits on the spot for the test result within an hour.
The Ministry of Health of the Czech Republic has also prepared a short instructional video, so you can see what will happen.
There is also an instructional video for general practitioners and specialists who would like to participate at the Covid-19 testing points.
Test safety and reliability
Tests are not dangerous if they are performed only by trained health professionals. Therefore, each sampling point has to be registered and healthcare professionals must be trained. We understand that a nasopharyngeal swab is not a pleasant thing. Hence, follow the doctor's instructions to ensure that the collection is successful and at the same time it will be at least uncomfortable for you.
Specificity and sensitivity calculations are used to determine the reliability and error rate of antigen tests.
Sensitivity is measured by the ratio of those tested positive by the antigen test to all those infected (including people whose tests are negative, even if the reference RT-PCR test tested positive). According to information from the press conference 26.11. 2020 (State Institute of Public Health - Ostrava), antigenic tests imported into the Czech Republic have a sensitivity ranging from 81% to 98%. Aforementioned means that a negative result from antigen testing does not necessarily mean that you are not infected with the same reliability as a PCR test.
Specificity is scaled by the ratio of those tested negative to the antigen test against all uninfected (including people who tested positive for the antigen test, even if the reference RT-PCR test was negative). Antigenic assays generally have a high degree of specificity. Here it means that a person who has tested positive for an antigen is most likely to be infected.
Can the testing be declined by a practitioner?
Yes. The testing is not carried out if the person supposed to be tested was isolated due to COVID-19 (at least for a minimal time span as stated in the current version of the Ministry of Health extraordinary measure regarding antigenic testing) and his/her first positive RT-PCR test result is less than 180 days ago. A fresh (max. 3 days ago) negative RT-PCR test result also poses a reason to decline antigen testing.