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Frequent Asked Questions​

Antigen is defined as any molecule that the defense mechanisms (immune system) identify as foreign to our body, which triggers the formation of antibodies that try to fight it.

Rapid antigen tests, which are commonly used in the diagnosis of respiratory pathogens, detect the presence of a specific viral antigen, implying a current viral infection.

Detecting the presence of the SARS-CoV2 virus (COVID-19) in a person’s body, therefore, allows the infection to be diagnosed on the spot, so that measures can be taken to prevent further transmission.

The optimal moment for the detection of Antigens is similar to that of RT-PCR, that is when their viral load (number of viruses) reaches the maximum concentration in the samples used (nasopharyngeal, oropharyngeal, salivary, bronchoalveolar).

For symptomatic patients, it would be from a few days before the onset of symptoms (2-3) and during the first 5-7 of their evolution.

For asymptomatic patients, viral load is most easily detectable from about 4-5 days after the onset of infection and for 7-10 days.

These times are approximate, they vary between different individuals and according to the quality/processing of the sample, as can be seen in published studies .

The information contained in this response is under continuous review based on updates from ongoing clinical studies and scientific evidence.

It is currently known that antigenic tests are especially accurate in symptomatic individuals, especially in the five days after the onset of symptoms, as well as in asymptomatic close contacts, in the first seven days after exposure to a confirmed case of COVID- 19. The margin of error with symptomatic people is low.

The latest published studies affirm that they are also effective in asymptomatic people, although the sensitivity rate is lower.

Rapid antigen tests are especially indicated for the rapid and efficient detection of patients infected by COVID-19 who live in environments where there is a high risk of community transmission (work centers, residences, schools, hospitals, etc. hotels, prisons, massive cultural and sports activities, etc).

Antigen tests are less accurate than PCR, but faster: 15 minutes instead of a couple of days, which could help control large disease outbreaks.

The saliva test in the studies provided by the manufacturer, provides a sensitivity of 97.3% and a specificity of 99.6% in a study on 500 patients.

PCR (polymerase chain reaction) is a laboratory test for diagnosing the disease. It is a molecular method based on the detection of the SARS-CoV-2 virus RNA by RT-PCR. At present, it is the reference technique for the diagnosis of the SARS-CoV-2 virus in the early stages of the disease. The molecular detection of the SARS-CoV-2 virus is very specific, therefore a positive confirms the detection of the virus. A negative result does not always mean the absence of the virus in our body since it depends on the moment of the disease, type of sample, processing of the same, etc. The antigen test is also a diagnostic test, but with some advantages; -R apidity in the confirmation of the results, between 5 and 15 minutes, while in the case of RT-PCR several hours may be necessary. -The logistics necessary for an RT-PCR is complex in terms of the necessary technical and human resources. -The cost (price) of a rapid antigen test is much lower than that of an RT-PCR. -All these advantages allow the antigen test to be repeated the number of times deemed necessary in time, to always maintain a safe environment and identify the infected patient before it generates community transmission.

This allows rapid antigen tests to be used for massive and preventive screening for the early detection of infected people and to guarantee safe collective environments.

Yes, there is no harm to mother or baby when a test is done.

In the interference study, the impact of possible components (such as different medicines or foods) that could interfere with the accuracy of the test results was evaluated, demonstrating a total absence of interferences in the saliva samples.

In the nasopharyngeal samples, the results showed that they did not have any interference with endogenous or exogenous substances, except a very weak one with HAMS Type I.

No, the more people who are tested, the better the extent (incidence / prevalence) of the COVID-19 virus will be understood, leading to better measures to prevent its spread.

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