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SARS-CoV-2, Antigen, Qualitative

Resumen:

Detecta antígenos del virus SARS-CoV-2.
Muestra: Otros
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What is the Coronavirus (SARS-CoV-2) Antigen Test

It is a laboratory test that can identify the virus that causes COVID-19 (SARS-CoV-2 virus) in secretions from the upper throat behind the nose (nasopharyngeal exudate), by detecting proteins that are part of the SARS-CoV-2 virus (specific antigen). The sample is taken with a swab.

What is it requested for?

To detect whether you are currently infected with the virus that causes COVID-19. If you are infected, you will be able to receive medical care and prevent infecting others.

When is it requested?

When you think you might be infected with COVID-19, either because you have symptoms or because you have been in contact with an infected person.

How long does it take from the onset of symptoms or from the probable time of infection for the test to detect the virus?

Experts suggest testing especially in patients who are symptomatic. In patients with symptoms, the maximum detection of the test is during the first 5 days of symptoms. Detection can still occur after this time but the sensitivity of the test decreases progressively as time passes. It is recommended not to use this test if more than 7 days have passed since the onset of symptoms as there is a greater likelihood of a false negative result. In patients without symptoms, a suitable period for testing may be considered to be between 5 and 12 days after the probable time of infection.

What does the test result mean?

Positive: it is highly likely that you are infected with the SARS-CoV-2 virus, which causes COVID-19. However, this test needs to be evaluated along with other tests. The results should be interpreted by your treating physician who will evaluate them together with your medical history, history and physical examination, and will be able to establish an appropriate diagnosis and treatment.
Negative: the test has not detected the virus, so it is likely that you are not infected. However, this test needs to be evaluated along with other tests and the results should be interpreted by your treating physician who will evaluate them along with your medical history, history and physical examination, and thus will be able to establish an appropriate diagnosis and treatment. If you have symptoms and the result is negative, you should continue to monitor your symptoms and obtain information from your physician about the need for isolation, repeat testing or other tests to confirm an infection.

What type of specimen is required?

The laboratory personnel should obtain a sample from the nose (upper respiratory tract), which consists of introducing the swab through the nasal cavity using a rotating motion and pressing on the walls of the nostril. The laboratory personnel will place the swab in a tube of extraction diluent.

How accurate is the test?

The accuracy is relatively high. According to the manufacturer, the sensitivity of the test is greater than 96% and the specificity is greater than 99%. Sensitivity is the ability to detect disease in infected patients. Specificity is the ability to give negative results in healthy patients.

I do not have any symptoms, is it necessary to test for Coronavirus?

It is recommended to avoid spreading the infection to your family, friends and colleagues. Research in the journal Science, learn more by clicking here, showed that two out of three infections of the new coronavirus have been caused by people who were not diagnosed with the virus or had no symptoms.

If it has been a short time since the probable time of infection (5-12 days), this test would be useful. If more than 12 days have passed, we recommend a serological test for antibodies.

Is the test painful to perform?

Obtaining the sample should not be painful, but it is uncomfortable. The sample collection takes less than 1 minute.

Is there a more accurate method to diagnose COVID-19?

Yes, in case you want to detect if you have an active infection, there are molecular tests, among them we have the one that uses a RT-PCR (Real Time Polymerase Chain Reaction) methodology, for more information about the test click on the molecular PCR link. In case you want to detect if you have been infected and have already overcome the disease, we recommend a serological test to detect antibodies: SARS-CoV-2 test, IgG and IgM, ELISA also called Coronavirus Elisa test or the rapid test. The antigen test will suggest whether you are infected now or not, however, it will not tell if you were infected in the past.

What are the similarities with the PCR molecular test?

For both the antigen test and the molecular test, the sample is taken with a swab.
The antigen test and the molecular test look for components of the virus, unlike the blood tests that look for antibodies generated by our body in response to SARS-CoV-2 infection.

What are the similarities with the isothermal molecular test?

In addition to having the same similarities as the PCR molecular test, the antigen test and the isothermal molecular test share the quality of being able to provide rapid results. What are the differences between the molecular tests (PCR and Isothermal)?

The antigen test is less accurate than the molecular test, especially if the result is negative.
The antigen test looks for proteins that are part of the surface of the virus, while the molecular test looks for the genetic material (RNA) of the virus.
The antigen test is a rapid test, i.e. it does not require processing equipment.
The antigen test has the advantage of being able to provide a faster result than a molecular PCR test.

Technical information and test limitations:

The SARS-CoV-2 antigen test by immunochromatography methodology allows the qualitative detection of SARS-CoV-2 specific antigens present in the human nasopharynx
It is a qualitative test. It does not provide information to quantitatively determine the concentration of SARS-CoV-2 antigens.
This test should not be used as the sole criterion for the diagnosis of SARS-CoV-2.
No laboratory test is 100% accurate. A positive test is a strong indicator that the specimen is from someone infected, but there is a possibility of a false positive result due to test performance or specimen contamination problems. A negative test does not completely rule out infection, and should not be used as the sole basis for patient management; these results should be combined with clinical observations (fever, cough, fatigue, etc.), patient history, and epidemiologic information.
As with all laboratory tests, the results should be interpreted by your treating physician, along with available clinical information.
If the result is negative and symptoms persist, you should seek guidance from your treating physician, who may indicate repeat testing or further evaluation.
A negative result does not at any time exclude the possibility of SARS-CoV-2 infection.