In addition to the tests we have discussed in previous articles, there are serological tests and self-diagnosis tests, which we will discuss in this article: other tests for diagnosis Covid.

Serological tests

These are tests that look for antibodies after exposure to the virus through a blood test or analysis.

Serological testing is usually performed after the person has overcome the disease. The test results will show what type of immunoglobulins the affected person has.

What are antibodies?

Antibodies are proteins that our immune system generates in response to an infection. They are responsible for “attacking” the microorganisms that cause an infection in order to eliminate them. When they are present in a blood serum sample, indicates that the person is going through the disease at that time or has had it previously. Antibodies may be present whether we have had symptoms or not.

After the test, the amount of antibodies can be analyzed. It has been seen that people who have passed the COVID-19 severe form, present high levels of antibodies compared to those who suffered it mildly.

If you want to know más of the duration of antibodies can read more here.

If the test result is positive, it will be confirmed that we have been in contact with the virus. The type of immunoglobulins present is then analysed.

What immunoglobulins can be given and what does the result mean?

Immunoglobulins M

IgM They appear early when we are fighting an infection. It is described that these appear from the 5th to the 7th day after infection. Its presence will last until we have recovered from the disease, approximately. Therefore, it is a marker of the acute phase.

  • If it is negative: it indicates that there is no contagion at that time
  • If positive: indicates that the disease is in the acute phase

Immunoglobulins G

These appear from the 14th day and they are the ones that indicate that the disease is being overcome, or has already been overcome.

  • If it is negative: it could indicate that there has been no infection, but you should remain alert since it could be that the infection is very recent, and the antibodies are shown in the result.
  • If positive: indicates that the infection was present, with or without manifestable symptoms.

In short, it means that:

  • If IgM or IgG are negative: there was no contact with the virus and there are no antibodies.
  • If IgM and IgG are both positive: the infection is activated and antibodies are beginning to be generated.
  • If IgM is positive and IgG is negative: at that time the infection is active, but the test will have to be performed again later to see if antibodies have been generated.
  • If IgM is negative and IgG is positive: the person was in contact with the virus and has shown or generated antibodies.

Self-diagnosis tests

In this other test of the tests that exist to diagnose Covid, it is not detected either RNA of the virus, but rather measures the amount of antibodies generated by our body.

The user performs the test on themselves by pricking their finger, similar to the glucose test used by diabetics. The results are obtained after a few minutes.

These tests are available in pharmacies. They can only be obtained with a medical prescription. They are not useful when there is a suspicion of infection because they do not detect the virus, but rather the subsequent response of our body in terms of the antibodies generated.

In these tests, it is very important to communicate the result to the doctor or health professional who prescribed the test.

We have already been warned; this type of tests They do not guarantee 100% that there is no possible infection. We must not relax or stop paying attention to the symptoms. In the case of having symptoms of an infection, or if there are doubts about whether the person is a possible infected person, it is recommended to do another test in the days following the negative result.

If you continue to have doubts about other tests to diagnose Covid or others related to respiratory health you can contact us by writing to us at info@happyair.org or call us at 91 822 78 74.

We invite you to join our community insp@ir Re-COVID where you can share experiences and ask questions to our healthcare professionals.

Author:
Teresa García Barredo, Respiratory Physiotherapist at the Lovexair Foundation and Coach HappyAir

Reviewers:
Eva Maroto López, Respiratory Physiotherapist at the Lovexair Foundation and Coach HappyAir
Lila Martínez Ucha, Communication Department of the Lovexair Foundation

Bibliography

COVID19 surveillance, control and indicators strategy
How PCR and rapid coronavirus tests work and how they differ
Coronavirus tests and differences between rapid COVID tests in Spain
SEIMC positioning on COVID19 microbiological diagnosis

Last updated on 7 March, 2026