Explanation of the different covid-19 tests

You can purchase the tests that we will talk about below in Kit & Test (Covid-19 autotest) and medmesafe (RT PCR for travel), for more information click here

Most of the questions received by the team of My test coronavirus, medmesafe and, kit and test; a good part refers to the differences between the different types of Covid-19 detection tests. We noticed the information circulating on social media is confusing, so we bring you a small guide to clarify the concepts.

About Covid-19

The SARS-CoV-2 virus was discovered in China in 2019. The most common symptoms associated with the disease it causes fever, fatigue, and a dry cough. It is difficult to know if a person has been infected before symptoms appear; so it is easy to spread the virus without knowing it.

What are the different tests?

We talk about the most common tests

1. TEST PCR (Polymerase chain reaction): The presence of the virus is detected through biological samples taken from the nostrils or throat of the patient. This test is used to identify people who are infected with the virus (whether or not they have symptoms). They have a very high degree of reliability and it is the most reliable test, but they have the disadvantage of being slow and expensive, apart from the fact that they have to be carried out in a laboratory and that their result depends a lot on the sampling process being carried out well.

Medmesafe has more than 50 authorized centers throughout Spain, to carry out PCR tests by qualified professionals, you can get more information by clicking here. If you are in the Community of Madrid, we offer you the PCR at home service, where we send a qualified nurse to your home or office to perform the extraction of the sample, and obtain the result of your test the same day, reducing the travel time and minimizing the risk of contagion, you can learn more at this link.

2. RAPID ANTIGEN TESTS: They are performed with respiratory biological samples from the pharynx or nasal passages (same extraction process as PCR) and seek to find coronavirus proteins. They are used to detect positive cases early and as a screening element for PCR. They are simple and cheap.

Recently, a lot of countries have authorized the self-test, if you want to acquire them please click here.

3. SEROLOGICAL TESTS: They do not detect the presence of the virus itself, but rather the antibodies that have been generated in the body in response to the disease. They are made from a blood sample and detect immunoglobulins IgM (early-onset antibodies) and IgG (late-onset and long-lasting antibodies). They seek to know if a person has been exposed to the virus and if they have recovered. They are simple, cheap and fast.

There are two types of tests in this category, ELISA (laboratory) and rapid serological tests such as the one proposed by https://www.mitestcoronavirus.com/ and which can be performed at home by a qualified professional. When purchasing a quick test, the manufacturer must be taken into account, since its quality can vary a lot from one to the other.

These tests can even detect mild or asymptomatic cases. For example, if there is the case of a person who has passed the disease without showing symptoms, they may have generated antibodies to the virus that indicate that they have passed it and that they have a degree of immunity to it. The main drawback of this test is that, by not detecting the virus itself, it does not give results if the patient is in an initial phase of the disease in which he has not yet generated antibodies.

This type of test is also used to identify population groups that have already overcome the disease, and, therefore, to determine a percentage of immunity and susceptible people in the population.

Test reliability:

The reliability of the tests depends on two indicators: sensitivity and specificity, and the combination of these give us the overall reliability.

Sensitivity: Measures the probability of having a positive test if the disease is present. The higher the sensitivity, the lower the number of false negatives. A possible cause of the appearance of a false negative could be that the individual has antibodies, but in such a low quantity that it is below the detection threshold of the test.

Specificity: Measures the probability that the test is negative in non-ill people. The higher the specificity, the lower the number of false positives. A possible case of false positive can occur if you have had a coronavirus infection similar to covid-19.

Reliability: The reliability or consistency of a test is its ability to produce the same results each time it is applied under similar conditions.

After explaining the different tests, we will try to answer another of the most frequent questions from our users:

Are the tests reliable?

Among the available tests, PCR is the most reliable, approaching 100%, antigen testing is a complimentary screening tool to PCR and it is very important to choose those with high reliability. Like the one at kit and test which has an overall reliability of 98%.

Why get tested?

Carrying out a test allows us to identify the presence of the disease, either by identifying the virus itself, its proteins, or the antibodies that our body generates to fight it according to the type of test carried out.

What we are looking for with these tests is the necessary information to be able to take the appropriate measures to protect both ourselves and others.

A person with Covid-19 can infect several other people on their own. One may have contracted the virus without developing symptoms and, by testing, be able to step back and make sure the virus does not spread.

When to get tested?

Depending on the state of the infection, it is recommended to do one test or another, in the first days it will be the PCR and then the serological one. The serological test is very interesting for people in whom the presence of the disease has been detected and who want to know if they have generated antibodies that can immunize them. It is also advisable, in case of positive, to repeat the serological test after a while to check if there are still antibodies or if they have disappeared.

Enrique Amores

Head of Software Development de medmesafe

Develop team leader - medmesafe Programmer - Telefónica Digital Education Programmer - Factory ETSIA SL