- Reference quantitative serological tests are performed using ELISA tests and determine cases of recent or past infection with SARS-CoV-2.
- These tests are of the utmost importance because they allow the evaluation and quantification of the presence of specific antibodies(immunoglobulins) against Spike protein that are correlated with neutralising antibodies (Nab) that determine immunity or protection against SARS-CoV-2.
- Type M antibodies (IgM) appear 5 days after infection.
- Type G antibodies (IgG) appear 10-15 days after infection.
- Blood (serum) collected in a dry tube
72 hours (3 working days)
Who should be tested?
The test should be done by anyone regardless of their age and gender.
When can I take the test?
In general, the test can be performed at any time and can be repeated. It is based on the detection of IgG antibodies. These are formed after contact with the virus. IgM antibodies can be detected in the blood after 5-8 days, whereas IgG are detected 10-15 days after infection. IgG titers are usually higher and more consistent than IgM titers.
For this reason, we recommend carrying out the IgG test 2 to 3 weeks after the onset of symptoms or presumed contact with SARS-CoV-2. If you have had no symptoms, a test may still be useful, as SARS-CoV-2 infection can also occur without symptoms.
What type of antibody test is used?
The ELISA tests we use are CE marked and are manufactured in Germany and detect IgG antibodies against the spike protein S1 (RBD) domain. IgG antibodies have the best possible specificity for the new coronavirus (SARS-CoV-2).
What is the specificity and sensitivity of the ELISA test used?
The ELISA test has a specificity of 98.6% and does not cross-react with other human coronaviruses, as it is directed to a specific region - the RBD - of protein S only present in SARS-CoV-2.
The sensitivity of the ELISA test depends on the time elapsed after infection according to the production kinetics of the IgG antibodies. So 22 days after infection the sensitivity is 95.3%, between 13-21 days after infection it is 90.5% and from 0-12 days after infection it is 69.4%. There is a small percentage of 4.7% of the infected population in which IgG antibodies are not detectable, even after 22 days of infection.