Although it seems that we know almost everything about COVID 19, both when it comes to preventing it and when it comes to recognizing the possible symptoms of this disease and its multiple side effects, in reality, as the virus evolves, many questions continue to arise, even more when we have been in contact with someone infected. Alerts of possible nearby infections, incubation times, phases of confinement, types of hydroalcoholic gels, masks, respirators, the evolution of possible different strains, vaccines in development and the countries that carry out the trials, the differences and similarities with other viruses, their multiple harmful effects, etc. When a person comes to get tests with us, many general doubts and many more specific ones continue to arise.

Here, we answer 10 of the questions that most often arise about the famous rapid test during the sample collection at our offices in Madrid.


1. What is a rapid antibody test?

A small prick on the finger, a drop of blood and a fifteen minute wait, this is a rapid antibody test. It is a very simple test that can be performed anywhere: at a wedding, in a social gathering, in an office or in your own home if required, since a laboratory is not required. Of course, always supervised by health personnel.

Rapid antibody tests do not detect the coronavirus but rather the immune reaction generated by our body after contact with the SARS-CoV-2 virus, that is, these tests detect the IgM and IgG antibodies produced by the person’s immune system against it. virus. They are indirect proof that the infection is active or has already been passed.


2. How are PCR tests different from rapid antibody tests?

The PCR test is capable of detecting the presence of the virus, the rapid antibody tests are not. The PCR test detects the coronavirus in the early stages of the infectious process, regardless of whether there are still no symptoms or they are not going to develop, as in the case of asymptomatic people. Another difference is the sampling: while in the rapid test a small sample of blood is extracted by pricking the patient’s finger with a lancet, in the PCR, epithelial cells and mucus are taken from the nose and mouth with a sterile swab, which will be later analyzed in the laboratory to check if they are indeed infected by the virus.


3. What do IgM antibodies indicate and what happens if the result is IgM positive and IgG negative?

IgM antibodies, indicated with an “M” in the test, are the first to be generated in our bodies during the infection phase. The detection of IgM antibodies, and in the absence of IgG, indicates that we are probably going through the acute or central stage of the infection. The level of these antibodies will decrease as we generate IgG antibodies, until they disappear.


4. When are IgG antibodies produced and what happens if the test is positive for IgG and negative for IgM?

Immunoglobulins G are produced in the later phase of infection and their presence indicates that we have protection against the virus. It is the most abundant type of antibody in our bodies and takes time to form after any kind of infection, being this case due to the SARS-CoV-2 virus. Its detection, and in the absence of IgM, indicates that we have completed the last stage of a viral infection and that we are in the resolution phase.

By the way, the “C” of the test indicates the quality control area and it always has to be activated for the test to be valid.


5. What happens if the test detects both IgM and IgG antibodies?

This case indicates a highly evolved infection and we are probably not cured yet, confirmation is required through a PCR test to know if, in fact, we are still in development or at the end of it.

However, a negative result does not exclude the possibility of SARS-CoV-2 infection. There are some  scenarios in which this is possible: the antibody concentration is lower than the minimum limit detected by the test or the antibodies against the virus have not yet developed at the time of taking the sample. The PCR test would be conclusive to know if there has been a recent infection, or not.


6. Are the results reliable?

Yes, in our laboratory absolutely. At Life Length we are proud to be able to offer the best and most effective antibody detection tests on the Spanish market, according to a study in collaboration with Yale University, with a sensitivity and specificity of 98.6% and 99.6% respectively. As you can imagine, the quality and precision of the tests is absolutely essential and it is terrible that the vast majority of the rapid tests that are marketed are not even remotely as reliable.


7. How long does it take to know the results?

As the name suggests, the results are obtained in just 15 minutes, although we will send you the report by email one hour after the test.


8. What is a serological test?

The purpose of a serological test is to know the previous exposure or presence of a pathogenic microorganism and, based on this, to check the individual’s response capacity to such infection, that is, the presence of antibodies against the virus in the blood. Some of the diseases most recognized by all and that are detected through serology are rubella, measles, viral hepatitis, HIV, toxoplasmosis, etc. At Life Length we perform two serological or antibody tests: the ELISA test, with results available in less than 4 working days, and the rapid antibody tests.

It is not necessary to come on an empty stomach to perform any of the tests to detect the presence of the coronavirus.


9. Should I combine a rapid antibody test with a PCR test?

When a person decides to take a COVID test, especially if they have had obvious symptoms, it is advisable to perform both types of tests, the PCR test and another one of the serology type, either the rapid test or the ELISA test. The rapid detection test for SARS-CoV-2 antibodies only indicates the presence of IgM and IgG antibodies and should not be used as the sole criterion for the diagnosis of infections by this coronavirus.

The combination of the two types of tests will tell us what phase of the disease we are in: in the first 15 days after infection, the PCR test will be positive and the serology negative; later, it will be the other way around: the serologies will be positive and the PCR test negative.


10. How much does it cost and where can I do a quick test?

The rapid antibody test price is 15 euros per person. The PCR price is 125 euros per person, the price for the rapid antigens test is 50 euros and the ELISA test price, 60 euros. You and your family can take the tests in Madrid, in our office at Calle Miguel Ángel number 11, on the second floor.

We also exclusively distribute our rapid antibody tests from a box of 20 tests and wholesale. If you are interested, see here the presentation about our tests or write to us at


Photographs: KirstenMarie, Life Length, Nick Fewings


Since the start of the COVID-19 pandemic, our laboratory has provided its comprehensive clinical analysis and testing services to help tackle the health crisis in Spain. We are working for hospitals, residences and corporate entities and we have contributed to the correct diagnosis of thousands of people and patients.

In our laboratory we carry out PCR tests to detect positive cases with a reliability of 99.9%, together with the rapid antigens tests and the most complete serology tests, the ELISA tests. We also offer the best quick antibody test for the detection of IgM and IgG antibodies against the SARS-CoV-2 virus, with a sensitivity and specificity of 98.6% and 99.6% respectively.