Do the COVID tests sold in pharmacies work?


The omicron variant COVID-19 has substantially increased coronavirus cases among Mexicans. It is common see long lines at health centers, IMSS, ISSSTE clinics and test centers deployed by the Ministry of Health and local health authorities to carry out tests, although very few are successful.

Faced with the inability of the public health sector to cope with the great demand for COVID tests, many Mexicans have resorted to looking for these supplies in laboratories, private hospitals, pharmacies and even on social networks.

Thus, for example, the secretary of Coahuila, Roberto Bernals Gómez, said that the COVID-19 antigen tests are good. “They are good, they cost 200 pesos and you let me endorse them, they are approved by international bodies,” he said.

The antigen test allows to identify a protein known as “S” or spike of the SARS-CoV-2 virus, the results are obtained in 15 to 30 minutes. But do they really work?

What does the WHO say about rapid antigen tests?

In this regard, the WHO has published an annual list of essential diagnostic tests since 2018, which contains the recommended in vitro diagnostic tests that should be available at points of care and in laboratories in all countries.

The latest edition, published a year ago, includes diagnostic tests for COVID-19 recommended by WHO (PCR test and antigen test).

In Mexico, Profeco ensures that “A positive antigen test result is considered accurate when the instructions are carefully followed, but there is a greater chance of having a false negative, which means that it is possible to be infected with the virus, but have a positive result.”.

In accordance with the Secretary of Health, the SARS-CoV-2 antigen detection tests are useful to detect specific molecules of the virus, which are present when there is an active infection, that is, when the person is ill at that time.

These tests can be performed directly at the point of care of sick people, such as in medical offices, health centers, care kiosks, among others. These tests are useful in communities with difficult access to a laboratory, and are recommended by the World Health Organization to complement epidemiological surveillance strategies for the SARS-CoV-2 virus epidemic..

The positive result of an antigen test can be used for the confirmation of COVID-19, in people who meet the requirements described above and does not replace the usefulness and use of molecular tests (RT-PCR).

COVID-19 home tests sold out

These types of tests are sold in pharmacies and cost approximately 200 pesos. However, at the moment they are sold out.

Besides, also Antibody tests are sold for approximately 320 pesos, although they are also sold out.

The antibody test, unlike the previous ones, serves to detect if a person has been infected by the virus and has developed defenses, and if the infection is still active or not. The presence of immunoglobulins IgM (which appear between 7 and 10 days after contact with the virus) and IgG (which appear between 10 and 15 days later) are analyzed.

A positive IgM indicates an active infection, while a positive IgG means that the infection is over. Although it is not used as a definitive diagnosis, it is useful to know if you have been in contact with the virus or to see the evolution of the disease in a confirmed case.

OA

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