Centres of Excellence -> Laboratory Medicine -> Serology testing for COVID-19 antibodies

Serology testing for COVID-19 antibodies

Serology testing enables determination of specific antibodies to the SARS-CoV-2 virus, and according to present knowledge, positive IgG antibodies to the SARS-CoV-2 virus suggests that a person had COVID-19 in the past or has been in contact with an infected person, or has developed antibodies after vaccination.

In our routine work, we use the most advanced ELISA (Enzyme Linked Immunosorbent Assay) methodology for the detection of IgG antibodies to the spike (S) protein of the SARS-CoV-2 virus. The sensitivity of the test (proportion of subjects with COVID-19) that we use in our institution, EUROIMMUN Anti-SARS-CoV-2 ELISA IgG, is 93.2%, while the specificity of the test (proportion of subjects without COVID-19) is 99.8%. These extremely high values ​​indicate the reliability of the methodology and testing (1, 2). Due to excellent correlation with the  First WHO International Standard (NIBSC 20/136), the results from the quantitative sample evaluation are expressed in International Units (IU/mL).

Serology testing by ELISA methodology is the best possible choice because, compared to rapid immunochromatographic tests (LFIA), ELISA has better sensitivity, specificity and positive predictive value (probability that subjects with a positive screening test truly have the disease) and the ability to obtain quantitative (numerical) results for the analyzed antibodies.

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The only way to determine if a person has developed specific antibodies after contact with the SARS-CoV-2 virus is serology testing. These antibodies are produced by B cells of the adaptive immune system, and recent scientific results indicate that IgG class antibodies appear in most subjects two weeks after infection and remain present in the blood (3).

In addition, in certain cases, especially in the late stages of COVID-19 development, when PCR methodology due to the lack of sufficient copies of SARS-CoV-2 virus is not sufficient to confirm the disease, serology testing remains the method of choice.

If you want to find out if you have had COVID-19 or have been in contact with an infected person, or you want to know the concentration of your antibodies after vaccination, serology testing will determine the existence and level of IgG class antibodies that target S protein (IgG S). The testing price is HRK 350,00. For reservation, click here LINK.


Testing is performed from a sample of peripheral venous blood. The patient must have fasted.


Testing can be done in our clinical chemistry laboratory (Branimirova 71E), with mandatory prior notice!



2. Dittadi R, Bertoli I, Carraro P. Reportable range of quantitative assays for SARS-CoV-2 antibodies determination. An overlooked issue? medRxiv 2021.03.21.21254043;doi:

3.  Rubio-Acero R,  et al. In search for the SARS-CoV-2 protection correlate: A head-to-head comparison of two quantitative S1 assays in a group of pre-characterized oligo-/asymptomatic patients. medRxiv 2021.02.19.21252080; doi:

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