This is how SalivaDirect works, the rapid covid-19 test 2:45
(CNN Spanish) -
At the beginning of the pandemic, scientists developed two tests to detect the coronavirus.
On the one hand, PCR, or the famous molecular test that requires a deep scraping with a swab in the nasopharyngeal cavity.
On the other, the serological one, which measures the amount of antibodies in the patient's blood.
Apart from these two tests, a saliva disease detection test and antigen tests have also been developed.
In this episode, Dr. Elmer Huerta talks about each of them.
You can listen to this episode on Apple Podcasts, Spotify, or your favorite podcast platform, or read the transcript below.
Hello, I am Dr. Elmer Huerta and this is your daily dose of information about the new coronavirus.
Information that we hope will be useful to take care of your health and that of your family.
Today we will see what advances have been made in tests to study covid-19, the disease caused by the new coronavirus.
In the episode of May 5 we said that there are two main categories of tests to study the disease.
The first discovers the virus in the body of the affected person, and the second, discovers the response of the body to infection by the virus.
How to detect coronavirus
In that May episode we mentioned only one test to detect the virus –– molecular or genetic––, but currently one more has been developed, the antigen test, which we will describe in a moment.
In summary, there are two tests to discover the virus in human secretions: molecular or genetic and antigenic.
For its part, the second category of tests, which discovers the response of the defense system to infection, includes serological tests, which have also improved in their ability to detect and measure the amount of antibodies that have been produced in response to infection viral.
Let's take a quick look at the two tests that detect the virus in a person:
The molecular test
The genetic or molecular test discovers segments of the genetic structure of the virus, using a technology called PCR that amplifies these segments and allows to recognize the RNA molecule of the virus.
This test is done by taking a sample of discharge from the throat, nose, nasopharynx, or saliva.
These PCR tests have the disadvantage of being invasive sampling, and requiring specialized personnel and equipment.
However, PCR technology has improved a lot in recent months, following the invention of systems that are faster and can be done in less sophisticated laboratories.
Even as we mentioned in the August 17 episode, Yale University has developed a saliva test that will cost just $ 10.
Much has been said about this test because it has received the support of the NBA and is used by its players and coaches.
The antigen test
For their part, antigen tests do not discover the genetic code of the virus.
They detect its protein envelope, more specifically its antigens or regions that stimulate the defense system.
Antigen tests are slightly less sensitive than molecular tests.
But because of its ease of use, its price and because its result can be read in just 15 minutes.
Therefore, it is considered that they will be the tests of massive use until an effective vaccine is found.
The FDA, for example, recently approved an antigen test from the Abbott laboratory that, unlike other existing serological tests, does not need any type of device to be processed.
The test will cost only $ 5.
The tests that detect the virus - both molecular and antigenic - are very important since they allow to identify the person who has the virus in his nose and throat.
This patient can then be isolated to protect his family and instructed to watch for symptoms that indicate that the disease may be complicating, such as respiratory failure, for example.
The other important use of genetic or molecular testing is that, by identifying the infected person, it allows them to identify their contacts, trace them for testing, and isolate them to prevent the spread of the disease.
In other words, the molecular test becomes a powerful public health instrument.
The serological test
For its part, the serological or rapid test is not done on the patient's secretions, but on his blood, and does not detect the virus, but rather the antibodies or immunoglobulins that the defense system of the infected person produced in response to viral infection.
The immunoglobulins that are produced in response to infection - and that are detected in the serological test - are of two types and are produced at different times during infection.
The first is a giant antibody called immunoglobulin M, which is produced at the end of the first week of illness, and the second is a smaller antibody called immunoglobulin G.
The rapid or serological test then discovers these two immunoglobulins, M and G, which give us some idea of the days that have passed after infection.
If the molecular and antigen tests made it possible to discover the infected person and their contacts, serology is a powerful public health instrument since it allows the study of the general population.
Mechanism of operation
Suppose, for example, that public health officials in a region want to know whether a certain neighborhood has already been affected by the disease.
Well, the most certain way to find out is to go to those neighborhoods and ask the residents to allow them to do the serological test.
This valuable information will be able to reveal, with a certain level of approximation, what is the prevalence of this disease in that community.
Unfortunately, since it is still unknown how long immunoglobulins G last, there is controversy as to whether serological tests can be used as a definitive proof that the disease will not return and so-called "immunity passports" can be issued.
In summary, the two categories of tests to study the infection by the new coronavirus include those that detect the virus -molecular and antigenic- and those others -the serological ones- that study the response of the defense system to infection by the virus.
Now that most countries are in the process of economic recovery.
Undoubtedly, in addition to masks, social distancing and hand washing, the judicious use of molecular or antigen tests - coupled with case and contact detection programs - will be the main method to control future outbreaks.
Do you have questions about the coronavirus?
Send me your questions on Twitter, we will try to answer them in our next episodes.
You can find me at @DrHuerta.
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Thanks for your attention.
If you have any questions you can send them to Dr. Elmer Huerta via Twitter. You can also head over to CNNE.com/coronaviruspodcast for all episodes of our “Coronavirus: Reality vs. Reality” podcast. fiction".
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