We are living the stage of "return to the New Normal" in which little by little our work and social routine is being reestablished. One of the main concerns that as a society we are interested in at this time is to know if after months of confinement is to know if the virus of COVID-19 has infected a person.
Much has been said lately about diagnostic tests for COVID-19, but what are they really for, or why are they so important?
Diagnostic tests for COVID-19 are done to determine if you are currently infected with SARS-CoV-2, the virus that causes Coronavirus 2019 disease, commonly called COVID-19.
There are several tests on the market, today, we will talk about the famous PCR test and why this test is, until today, the most effective test for the detection of COVID-19.
PCR or molecular tests:
This type of test, called PCR, detects the presence of genetic material of the virus (RNA) through samples taken from the person's respiratory secretions. To date, they are the most recommended tests by the World Health Organization (WHO) and the United States Food and Drug Administration (FDA) for diagnosing coronaviruses. These tests are usually very accurate when performed in certified laboratories by highly trained personnel.
How does PCR work?
The test begins with the collection of fluid from the nose or throat with a swab. The results are given in minutes if analyzed in the same place.
The swab is placed in an acidic liquid solution that has been heated to very high temperatures (132.8oF / 56oC), which causes the SARS-CoV-2 virus envelope to break down, exposing its viral RNA. The RNA is then amplified hundreds of millions of times to make the virus detectable.
Molecular tests are considered very accurate when it has been done properly by a trained person.
“Rapid Tests” Antibody and Antigen Testing: Are antibody tests as effective as PCR?
No. These tests detect the presence of antibodies in the blood, however, this test tells you the immune response generated but does not detect the presence of the virus.
There are two types, the serological, in which a blood sample is obtained and processed by a laboratory, the result can take between 12-24 hours; and the rapid tests that use a small drop of blood, do not require a laboratory process and their results are fast, hence their name, both detect the presence of IgM and IgG antibodies.
The disadvantage of these tests is that they are not able to detect the virus in the early stages of infection, so they are usually negative in the first few days after starting with suspicious symptoms, i.e. they have a high rate of false negatives.
Currently, they are not recommended for diagnosis of recent COVID-19 infection because of their low specificity.
What should I do if I am interested in having a PCR test for COVID-19?
Contact your doctor and talk about your situation. Your doctor will tell you if he or she thinks you need a test for COVID-19. Also, don't forget to describe any symptoms you have.
What does it mean if the sample is positive for the virus that causes COVID-19?
If you tested positive for COVID-19, it means you currently have the virus. You must watch your symptoms carefully.
Take the following steps to avoid spreading the virus:
Contacting your treating Doctor
Follow quarantine rules and stay at home (do not go outside unless you need medical attention)
Maintain a social distance even from other people in your home
Wash your hands constantly
Cover your nose and mouth when you touch or sneeze
Frequently cleans and disinfects common surfaces such as telephones, controls, tables, door handles, water faucets, etc
What does it mean if the sample test is negative for the virus that causes COVID-19?
A negative result for this test means that SARS-CoV-2 RNA was not present in the sample above the detection limit. However, a negative result does not rule out COVID-19 and should not be used as the sole basis for treatment or patient management decisions. A negative result does not exclude the possibility of having COVID-19.
When diagnostic tests are negative, the possibility of a false negative result should be considered in the context of a patient's recent exposures and the presence of clinical signs and symptoms consistent with COVID-19. A false negative result should be considered, especially if a patient's current exposures or clinical presentation indicate that he or she is likely to have COVID-19. It is recommended that the test be repeated on the fifth and tenth day after the onset of symptoms or date of exposure.
You should still follow guidelines for handwashing, constant surface disinfection, face mask use (mouth/nose), and social distancing.
How is COVID-19 transmitted?
A person can get COVID-19 from contact with another person who is infected with the virus. The disease can spread from person to person through droplets from the nose or mouth that are released when an infected person coughs, sneezes, or speaks.
Remember, whether the test is positive or negative, it is essential to continue to take preventive measures for the sake of your health, those around you, and everyone else.
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