General Practice 2022

COVID-19 tests: when to do it, types and results

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COVID-19 tests: when to do it, types and results
COVID-19 tests: when to do it, types and results
Anonim

There are different types of tests for COVID-19 that allow us to know if a person is infected with the coronavirus or if, at some point, they have already had contact with the virus, having developed temporary immunity.

The only test capable of confirming active COVID-19 infection is the RT-PCR exam, in which a sample of secretions is taken, through the nose or mouth, and analyzed in the laboratory, confirming or not, the presence of the virus in the body. Any other test for COVID-19 is not considered by the WHO to be a diagnostic test for COVID-19 and is only used to identify people who have already had contact with the virus and may not have an active infection at the time of the test.

In addition to these tests, and if the person shows signs of infection with the coronavirus, the diagnosis of COVID-19 may also include performing other tests, mainly blood count and chest tomography, to assess the degree of infection and identify if there is any type of complication that needs more specific treatment.See which symptoms may indicate infection by COVID-19.

Swab for COVID-19 test

Swab for COVID-19 Test

1. When to test for COVID-19?

The time to take the COVID-19 test varies according to the type of test that will be performed:

  • Quick test: you should wait, on average, 2 days for the antigen test and the self-test, and at least 8 days for the quick test of antibodies.
  • RT-PCR: should be performed between the 3rd and 7th day after the onset of symptoms.

Regardless of the type, it is always important to inform the he alth authorities in case of suspicion of infection, to know how to proceed and what is the best test to do.

2. Who should be tested for COVID-19?

Rapid tests can be done by anyone to identify if they have already had contact with the new coronavirus, but they do not serve to confirm the diagnosis of COVID-19.See more details about rapid tests for COVID-19 or take the online symptom test to know your risk of having COVID-19.

On the other hand, the secretion exam (RT-PCR), which is the only one capable of confirming the infection by COVID-19, must be performed by those who present symptoms suggestive of the infection, to confirm the diagnosis, or in cases in which that the rapid test showed a positive result.

3. What tests are there for COVID-19?

There are three main types of tests to detect COVID-19:

  • Examination of secretions (RT-PCR): must be performed in a laboratory or he alth institution and is the only method considered by the WHO as a reference in the diagnosis of COVID-19. It is done by collecting secretions using a swab, which is similar to a large cotton swab;
  • Blood test (serology): analyzes the presence of antibodies to the coronavirus in the blood and, therefore, serves to assess whether the person has already had contact with the virus or if there are antibodies to the infection;
  • Rapid tests: can be done at the pharmacy, present results in 15 minutes and assess the presence of antibodies to the new coronavirus or antigens. Depending on the type of rapid test, it is possible to know if there is a risk of the person being infected or if they have already been in contact with the virus;
  • Self-test: is a type of rapid test that the person can perform himself and which aims to identify the presence of the SARS-CoV-2 antigen, giving the result in about 15 minutes and serving as a screening. It is important that the positive self-test result is confirmed through the RT-PCR exam and that the negative result is re-evaluated, especially in the presence of signs and symptoms suggestive of COVID-19.

There is also the rectal exam, in which a swab is used that must be passed in the anus. However, it is an impractical and inconvenient type of test, not being indicated in all situations.Rectal examination for COVID-19 has been indicated for the follow-up of some hospitalized people who have a positive nasal swab, because some studies suggest that a positive rectal swab is associated with more severe cases of COVID-19.

4. How does the quick test work?

Rapid tests for COVID-19 are a way to obtain faster information about the possibility of having a recent or old infection with the virus, because the result is released in about 15 minutes.

This type of test aims to identify the presence of antibodies that have been produced against the virus or antigens, which are proteins of the virus itself.

Often, the rapid antigen test is used as the first stage of diagnosis, being complemented by the RT-PCR exam when the result is positive. The rapid antibody test is used to find out if the person has already been in contact with the virus or has developed immunity after vaccination, for example.

Better understand what the quick test is for, when to do it and results.

5. Which test can be done at the pharmacy?

Pharmacy tests are of the rapid type, that is, they allow the identification of antigens or antibodies produced against COVID-19, being useful to understand if you have already been in contact with the virus. However, to confirm that there is currently an active infection, an RT-PCR examination of secretions is necessary.

6. How to do the self-test?

The self-test is a type of quick test that is simple to do, it is only important that the person follows the instructions contained in the test package and that they disinfect their hands before starting the test. In general, the self-test step-by-step is as follows:

  1. Open the self-test kit from the packaging and open the swab by the end, avoiding touching the part containing the cotton;
  2. Tilt your head back and insert the swab about 2 cm;
  3. Rotate the swab inside the nostril for about 10 to 15 seconds and then insert it into the other nostril, repeating the movement;
  4. Place the swab in the container containing the liquid and rotate about 10 times;
  5. Remove the swab, place it carefully inside the package, dispose of it in a suitable trash and close the container containing the liquid;
  6. Open the test cassette package and place 4 drops of the liquid that was in contact with the swab;
  7. Wait about 15 minutes to check the result, which is given by the appearance of 2 lines in the test.

If the result is positive, it is important that the RT-PCR test is performed to confirm the infection, since the self-test is not considered diagnostic, serving only as a screening. In addition, the fact that the result is negative does not rule out the possibility of SARS-CoV-2 infection, as the test may have been poorly performed or performed at a time when the viral load was very low.Thus, in the presence of signs and symptoms suggestive of COVID-19 and a negative self-test result, for example, it is important that other tests are performed to assess the infection.

See how to understand the self-test result.

7. How long does it take to get the result?

Rapid tests usually take between 10 and 30 minutes to be released, while the results of blood tests or RT-PCR can take between 12 hours to 7 days to be released, depending on the laboratory and the technique used.

The ideal is always to confirm the waiting time together with the laboratory, as well as the need to repeat the exam.

8. What does the result mean?

The meaning of the results varies according to the type of test:

  • Examination of secretions (RT-PCR): a positive result means you have COVID-19;
  • Blood test (serology): a positive result may indicate that the person has the disease or has had COVID-19, but the infection may no longer be active;
  • Quick test: a positive result may indicate that you are infected or that you have been in contact with the virus, depending on the type of rapid test. See more about quick test types and results.

It is important to note that a negative result does not mean that you do not have the infection, especially if the test was done on people without symptoms or within 8 days of the onset of symptoms. There are cases where it can take up to 10 days for the virus to be identified in the tests. Thus, ideally, in case of suspicion, all necessary measures are taken to prevent transmission of the virus, in addition to maintaining social distance for up to 14 days.

See all the important precautions to prevent the transmission of COVID-19.

9. Is there a chance the result will be "false"?

The tests developed for COVID-19 are very sensitive and specific, so there is a low probability of error in the result.However, the risk of getting a "false" result is greater when tests are performed before the indicated period, as it is likely that the virus has not replicated enough, nor stimulated an immune system response, to be detected.

Also, when the sample is not collected, transported, or stored correctly, it is also possible to get a "false negative" result. In these cases, the test must be repeated, especially if the person has signs and symptoms suggestive of infection, if they have had contact with suspected or confirmed cases of the disease, or if they belong to a risk group for COVID-19.

Thus, in case the person has symptoms of COVID-19 and the test is negative, the doctor may indicate the performance of other laboratory tests that may suggest the infection, such as the C-reactive protein dosage, D-dimer, fibrinogen, lactate dehydrogenase (LDH), bilirubin and albumin, in addition to a blood count and, in some cases, a chest X-ray.

It is important that the person who has had a negative test for COVID-19 but who has symptoms remains in isolation, because they can be a carrier of other easily transmitted viruses, such as Influenza, and can transmit it. it to other people.

What to do in case of COVID-19

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.
  • Restart

    • I have no symptoms.
    • I only have mild symptoms (fever, cough, tiredness, headache, sore throat, loss of tasteā€¦).
    • I have moderate symptoms (very intense cough, some shortness of breath, excessive tirednessā€¦).
    • I'm really short of breath.
    • Restart

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    • No.
    • I did a self-test
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    • I did RT-PCR test.
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    • test=0"' > Negative
    • test=1"' > Positive
    • Restart

      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 individual protection measures (such as wearing a mask and avoiding unnecessary travel) and be aware of the appearance of symptoms in the next 14 days.

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