Morocco is preparing for the implementation of antigenic tests which have many additional advantages to PCR tests.
An evaluation of three different antigenic tests is underway at the Pasteur Institute in Casablanca at the request of Minister Khalid Aït Taleb.
The decision to introduce rapid antigenic tests is all the more relevant given that Morocco is currently in the phase of active circulation of the virus in several cities or regions and that it is preparing for the winter wave. That the WHO foresees as being probably very strong in the northern hemisphere. This recourse of rapid antigenic tests has also been requested for several weeks by learned societies and in particular the Moroccan Society of Medical Sciences.
Several international laboratories are producing rapid antigenic tests against Covid-19. Morocco has pre-selected three tests that it is currently evaluating, confirms the Pasteur Institute in Casablanca. The evaluation consists of verifying the sensitivity and specificity of each test, on samples of “sufficient” size within the Moroccan population.
The verification is carried out with consenting and informed persons. A sample is taken from each of these people. This sample is then partly tested by the gold standard, that is to say, the PCR and partly by the antigen test. The results are then compared.
The objective is to determine on the Moroccan population, to what extent this test is sensitive to the presence of antigens and to what extent it is specific (to the SARS-CoV-2 coronavirus). For the WHO, antigenic tests must have a sensitivity of at least 80% and a specificity of at least 99%.
These tests are increasingly recommended during periods of active virus circulation.
As a rule, these rapid antigenic tests are performed in doctor’s offices, pharmacies, clinics, hospital emergency rooms, medical analysis laboratories, in the presence of the patient. We have not been able, at this stage, to know if this test will be used at airports.
The result is delivered after 15 to 20 min. Obtaining the result is easy, it is performed by a laboratory assistant or nurse. On the other hand, the sample is in all cases tested in Morocco, nasopharyngeal, identical to the sample for PCR test.
WHO and public health authorities in several countries have in the past recommended rapid antigenic tests in very specific cases linked to the presence of comorbidity, advanced age and therefore vulnerability or symptoms that do not allow any waiting for 24 hours or 48 hours for a PCR test. The goal is to save time, speed up treatment and therefore reduce the risk of worsening cases.
Currently, faced with the increasingly rapid circulation of the virus, several countries are considering the use of antigenic tests for mass detection because the number of PCR tests carried out cannot increase with the same rapidity as the number of cases.
According to unofficial sources, Morocco plans to use these large-scale antigen tests in the event of a second abrupt and strong wave as feared, this winter.
The aim would then be to improve early detection, to facilitate the differential influenza-Covid diagnosis; to carry out targeted screening (people over 65, people vulnerable to comorbidity, nursing staff, contact cases, factories, universities, etc.).
The result of the PCR is not only slow, but in addition, this test is indicated only beyond 4 days after the appearance of the first symptoms. On the other hand, the antigen test can be carried out before these 4 days.
To summarise, the antigenic tests are used for operations of rapid diagnosis or of diagnostic orientation according to the cases. In the absence of symptoms and for the general population, use will depend on the strategy followed and the speed of circulation of the virus. It is recommended to start with target populations such as vulnerable or at-risk people. In the case of patients with symptoms, antigen testing is done in cases where the doctor prefers not to wait for the result of a PCR.
The same goes for hospital emergencies or for contact cases or finally on an outpatient basis.
The last category of use will be to differentiate, in a doctor’s office or in the emergency room, a case of Covid from the flu.
