You have probably wondered more than once why there are several kinds of covid-19 tests and what each of them is currently used for.
Today's article is not to be missed! We will tell you why there are different covid-19 tests, what is the purpose of each test, their main features and another very important fact to keep in mind, their limitations, to this date, no covid test is 100% accurate.
Last year, with the arrival of the pandemic caused by Covid-19, covid tests began to be carried out with the main objective of reducing the spread of this virus, detecting people with positive results in order to maintain a subsequent mandatory quarantine and avoid possible future infections with people in their environment.
There are several tests for the detection of Covid-19 determinants:
- At the individual level: whether a person is infected with the virus or has already overcome it and has immunity.
- At the population level: when there are outbreaks of Covid-19 in a specific location.
How do the covid-19 tests work?
A covid test is intended to detect the presence of Covid-19 due to an active infection in a person's body. The different types of covid tests have two factors in common: specificity and sensitivity.
On the one hand, specificity is considered to be the chance that a healthy subject will have a negative covid test result. In other words, it is a total percentage of negatives. The higher the specificity, the lower the number of false positives.
On the other hand, the sensitivity is the ability of the covid test itself to detect the virus, or in other words, the percentage of positives or a positive test.
Currently there are different tests for the detection of Coronavirus but for different purposes depending on what we want to know.
What Covid-19 tests exist and what they are used for?
We will now tell you about the most common Coronavirus tests, their limitations and much more!
PCR test
The PCR (Polymerase Chain Reaction) is the most reliable test for the detection of Coronavirus. Its function is to detect active Covid-19 infection through a swab sample inserted into the nostrils or throat. This sample is sent to the laboratory for examination, which can take several hours. If the result is positive, it means that the person is infected with Coronavirus but it will not be possible to know if the person has already overcome the virus.
This type of test is characterised by being specific and highly sensitive, which is why specialised technical personnel are required: it can detect the virus in people who are not yet showing symptoms but who are already infected, and also in other cases it occurs, obtaining a positive PCR and being asymptomatic and not contagious. This happens when they have been symptom-free for more than 14 days and their body has developed antibodies.
Limitations of the PCR:
- Sample collection must be correct. For example, if the disease has reached a specific part of the body such as the lungs, it will not be detected and the result will be negative.
- A positive test result does not indicate that the person is still carrying the virus and can spread it.
Covid-19 antigen test
The antigen test is another type of nasal or saliva sample test (depending on the instructions for use of each test) for the detection of Coronavirus. This test detects a protein that is present in the virus. The most striking feature of the antigen test is its speed, as it takes only 15 to 20 minutes to obtain the results.
As with the PCR, it is also unable to detect whether the person has already overcome the virus.
Limitations of the antigen test:
- The antigen test may not detect low levels of virus and the result may be false negative. The results of these tests should be interpreted taking into account that during the first 7 days after infection the viral load is at its highest point.
At Dentaltix we have antigen tests available with nasal swab or saliva sample collection, see below!
Boson Biotech Covid-19 Antigen Self-diagnosis Test
Easy to use Covid screening test providing fast results in as little as 15 minutes.
Features of the Boson Biotech GSD NovaGen SARS-CoV-2 Antigen Test:
- Immediate and safe solution.
- High accuracy
- Easy to use
- No equipment required
- Nasal swab antigen test
- Contents: 1 single-use test (cassette), sterile nasal swab, extraction tube, pot of solution and instructions for use.
Interpretation of results:
- Negative: A coloured line appears in the region of the control line (C). No line appears in the test region (T).
- Positive: Two coloured lines appear. A coloured line appears in the control line region (C) and an adjacent line appears in the test region (T).
- Invalid: The control line does not appear. Probably insufficient sample volume or incorrect procedural techniques.
New Gene saliva-based Covid-19 Antigen Rapid Test
Test designed for the detection of antigen against Covid-19 through saliva samples. This test will allow you to perform it on your patients in a very fast and highly efficient way.
Features of the New Gene Covid-19 Antigen Test:
- Bloodless test
- High accuracy
- Easy to use
- Quick detection with results in 15 minutes
- Specificity of 99%
- Available in 1 or 25 units
- Content: 1 container for saliva sample, 1 stick, 1 tube with reagents and 1 device to analyse the sample in minutes
Interpretation of the results:
- Negative: 1 purple line appears at the top (C).
- Positive: 2 lines appear at (T) and (C).
- Invalid: No lines appear or when only one line appears in (T).
Differences between PCR and antigen testing
You have probably often wondered what are the differences between PCR and antigen testing. Well, as you already know, both tests are used to detect whether a person is positive for Covid-19 but they have some interesting differences:
- Time: a factor that varies in terms of knowing the results. As the PCR test is sent to the laboratory the results take longer (up to 48 hours). However, the antigen test gets results in as little as 15 minutes.
- Sensitivity to symptoms: PCR detects the virus with minimal viral load, whereas the antigen test does not.
- Reliability: PCR is the test that gives the most reliable results, especially, as mentioned in the previous point, when the viral load is very low.
Covid-19 antibody test
The covid antibody test detects the various classes of antibodies to Covid-19 in blood samples. In other words, these tests detect a person's immune response, not the presence of the virus. This test detects 2 classes of antibodies: IgM (antibodies that appear in the early phase of infection and disappear weeks later) and IgG (antibodies that appear in the late phase of infection and remain in the body for several months or even years).
The purpose of the covid-19 antibody test is to determine whether there is or has been an immune response to the virus. In addition, there are 2 types of antibody tests: rapid tests or serological tests in venous blood (ELISA / CLIA). The main difference is that rapid tests give results in 10-15 minutes on a capillary blood sample and serological tests are performed on a venous blood sample and are analysed in a laboratory, so the time taken to obtain results is longer.
Limitations of the covid-19 antibody test:
- Sometimes it takes several weeks to detect the level of antibodies in the body, so a person can have the virus and still test negative for it.
- Antibody tests are in the research phase and are currently trying to find out if the antibodies that are detected protect the body from possible future infections.
SARS-CoV-2 antibody detection test INgezim Covid 19 Crom by Eurofins Ingenasa
The covid-19 antibody rapid test is able to detect specific antibodies against SARS-CoV-2 in serum and blood samples.
Features of the Eurofins Ingenasa antibody detection test:
- Specificity of 99.3%
- Sensitivity of 94.5%
- Easy to use
- Results in 10 minutes
- Can be carried out outside the laboratory
- Content: 5 individually packaged immunochromatographic devices, blister of 5 single doses, 6 micropipettes and 6 lancets
Interpretation of results:
- The membrane contains a test line (T), on which the N protein of SARS-CoV-2(3) is immobilised; and a control line (C), formed by an antibody specific to the control protein(4). If antibodies to SARS-CoV-2 are present in the sample, they will react with the black latex particles coated with the N protein.
- The latex particle/protein/antibody complex will migrate and bind to the protein contained in the test line, resulting in a coloured line.
- If the sample does not have antibodies to SARS-CoV-2, no colour will appear on the T line.
Frequently asked questions about the Covid-19 tests
As you already know the different types of covid tests that exist and what each one is used for, we are going to clear up some possible doubts you may still have. Let's get to the Q&A!
➜What does a positive, negative or invalid covid test result mean?
A positive result is synonymous with active infection, a negative result could be that there is no infection or it is incubating. And an invalid result occurs when the sample has been insufficient or the process has not been performed correctly.
➜Can you get a positive PCR and a negative antigen result?
The answer is yes as the antigen test is less sensitive than the PCR.
➜What is a "false negative"?
A negative result in people who do have COVID-19 and can even happen if the viral load is minimal.
➜Which covid tests are most recommended?
If we want to know if a person has the virus at that very moment, a PCR or a rapid antigen test is best. If, on the other hand, we are interested in finding out if we have already passed the Coronavirus infection, the best is an antibody test.
➜If the covid test result is positive, what should you do?
Even if you have no symptoms and your result is positive for Covid-19, you should immediately self-isolate and contact the relevant health services in your autonomous community.
Below, we present you a table where we compare the different covid tests so that you can have a clearer picture!
That's it for today's article on the different covid-19 tests! What did you think? It is very important to be aware of what each one is for depending on the situation and to know how to interpret them. Share with us any doubts or concerns you may have and we will be happy to help you.
Last TIP! Keep protecting yourself against Covid-19 at your dental clinic.
For more news and updates from the dental industry, remember to visit our social networks and our blog articles section. Don't miss a thing!