Test rápid COVID-19: as é done, where to do and results

How it's done: a sample of saliva or nasal secretion is collected using a swab, which is similar to a cotton swab. The sample is then diluted in a special liquid and placed in a small plastic device, similar to a pharmacy pregnancy test. When the virus is present, the test strip changes color or has two stripes.

The rapid antigen test can be done in pharmacies, testing centers and in laboratories, being carried out by he alth professionals, or at home through the self-test, in which the person collects himself, performs all the exam procedures and interprets the result, being essential to follow all the instructions to avoid that the result is wrong. Learn more about self-testing for COVID-19.

How to read the result: after 15-30 minutes, if the absorbent tape has a stripe on the test field "T", even if it is soft, it means that the result is positive and the person has a high probability of having an active infection. If only a stripe appears in the "C" control field, the result is negative. If there is no line in the "C" field, the test is considered invalid.

How it works: this type of rapid test detects the presence of coronavirus proteins, which are antigens. The antigens are only present when the coronavirus is actively multiplying.

It is important to note that the result of this test is not altered by vaccination. This is because the vaccine only exposes a small part of the virus to the immune system, not being enough to be identified in the antigen test.

2. Rapid antibody test

What it indicates: if the person has antibodies to the disease, which may indicate that they have had contact with the coronavirus at some point.

How it's done: is done by collecting a drop of blood on the finger. This blood is then placed in a small plastic device along with a solvent.

How to read the result: after 15-30 minutes, if the absorbent strip has a streak for IgG (G) and/or IgM (M) antibodies, even if it is mild, means that the person has antibodies against COVID-19. If only a stripe appears in the "C" control field, the result is negative. If there is no line in the "C" control field, the test is considered invalid.

How it works: analyzes the presence of IgG and/or IgM antibodies in the blood, which are proteins produced to defend the organism. COVID-19 antibodies are produced over days or weeks after a person has been infected.

It is important to note that the rapid antibody test should not be used to identify whether the person has developed immunity after vaccination.

When to take the quick test

The indicated time to perform the COVID-19 rapid test varies according to the type of test:

Rapid antigen test (nasal): is indicated for people who have had symptoms of COVID-19 for at least 2 days;
Rapid antigen test (oral): is indicated for people who have symptoms of COVID-19, between the 1st and 7th day of suspected infection;
Rapid antibody test (blood): is indicated for people with symptoms of COVID-19 for more than 8 days, people who have had contact with people who are COVID positive, people who want to know if they have had COVID-19 before or for people who have tested positive for COVID-19, have been cured, and want to know if they have antibodies to the disease;

Rapid COVID-19 tests are less sensitive than laboratory-based RT-PCR tests and may give a false negative result. This means that a negative result in the rapid test does not eliminate the possibility of the person being infected with the coronavirus, and it is recommended that the results are always evaluated by a he alth professional, along with analysis of the symptoms presented and other tests such as blood count and chest tomography..

Where to take the quick test

Rapid tests for COVID-19 are approved by ANVISA to be carried out, without a prescription, in laboratories, testing centers, pharmacies and drugstores that have safety measures and he alth professionals trained to carry out sample collection and interpretation of results.

In addition, there are also "self-tests" which are quick tests that can be done at home, by collecting a nasal sample. However, to ensure a more reliable result, it is always recommended that the self-test be performed in the presence of a he althcare professional.

What does the result mean

The meaning of the result depends on the type of test performed:

Test type	Positive result	Negative result
Rapid antibody (blood)	The person has antibodies to COVID-19. This means that you may have an active infection or that, at some point, you have been infected.	The person has no antibodies. Which may mean that you have never had contact with the coronavirus; who has already been infected but has not produced enough antibodies; or who has an initial infection and has not yet produced antibodies.
Rapid antigen (nasal/oral)	Virus particles have been identified and therefore it is very likely that the person has COVID-19. An RT-PCR exam is required to confirm the result.	No virus particles identified. This may indicate that the person does not have COVID-19 or is at an early stage of infection, where there are not enough particles to be identified in the test.

It is always very important to remember a negative result does not exclude the possibility that the person is infected with the coronavirus, especially if they have symptoms suggestive of the infection, such as fever, dry cough, tiredness, loss of taste or sore throat. See the main symptoms that may indicate COVID-19.

Regardless of the result, after carrying out a rapid COVID test it is important to maintain all preventive care, such as wearing a mask, regular hand washing and social distancing.

What to do in case of COVID

If you test positive for COVID-19, have been in contact with someone infected or have symptoms suggestive of the infection, please fill in your details to find out what to do:

option=b, @block-A1"' > I tested positive for COVID-19.
option=c, @block-A1"' > I have symptoms suggestive of COVID-19.
option=d, @block-A1"' > I've been in contact with positive case.
option=f, @block-F1"' > I've had COVID-19, but I still have symptoms.
option=e, @block-A1"' > I want to know more information.

country=en, @block-B1"}, {"condition":"option=c", "action":">country=en, @block-C1"}, {"condition":"option=d", "action":">country=en, @block-D2"}, {"condition":"option=e", "action":">country=en, @block-E1"}]' > Portugal
country=br, @block-B1"}, {"condition":"option=c", "action":">country=br, @block-C1"}, {"condition":"option=d", "action":">country=br, @block-D1"}, {"condition":"option=e", "action":">country=br, @block-E1"}]' >

Self-test.
Rapid antigen test.
RT-PCR.

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I have no symptoms.
I only have mild symptoms (fever, cough, tiredness, headache, sore throat, loss of taste…).
I have moderate symptoms (very intense cough, some shortness of breath, excessive tiredness…).
I'm really short of breath.

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No.
I did a self-test
I did a rapid antigen test.
I did RT-PCR test.

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test=0"' > Negative
test=1"' > Positive

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It is possible that your symptoms are a sign of another infection, such as the flu or H3N2, for example. Still, we advise you to repeat the COVID-19 test within the next 3 days. Check out the differences between flu, COVID-19 and a cold.

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risk=1, @block-D5"' > I live with the person who tested positive.
I have been in direct contact with the positive person (less than 2 meters) for more than 15 minutes and I am a he alth professional or work in an institution for the elderly.
risk=0"' > The person who tests positive does not live with me.

Restart

Yes.
No.

Your contact is considered high risk. You do not need to isolate yourself, but you must maintain all personal protective measures for 14 days, be aware of the appearance of symptoms and perform a COVID test as soon as possible (rapid test or RT-PCR). If the result of the 1st test is negative, you must repeat the test between the 3rd and 5th day after contact with the positive person.

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Your contact is considered low risk. For this reason, you don't need to do isolation, or perform COVID test. However, you must maintain all personal protective measures (such as wearing a mask and avoiding unnecessary travel) and be aware of the appearance of symptoms in the next 14 days.