22/05/2020
Immunology testing for COVID-19
Immunology (serology) testing for SARS COV-2 is at increased demand in order to better quantify the number of cases of COVID-19, including those that may be asymptomatic or have recovered. Serology tests are antibody-based blood tests that can be used to identify whether people have been exposed to a particular pathogen by looking at their immune response.
Antibodies, also called immunoglobulins (Igs), are proteins produced by the immune system in response to an infection and are specific to that particular infection. The foreign stimulant is called antigen (Ag). A wide range of substances are regarded by the body as Ags, including disease causing organisms (bacteria, viruses etc.) and toxic materials such as insect venom. Specific proteins (Ag) from SARS-CoV-2 stimulate the immune system to produce an immune response, and corresponding antibodies (Abs) appear in the blood. Abs recognize and latch onto Ags (like a lock and key) in order to remove them from the body. A type of Ab, called IgM, appears first, and is mostly positive within few days of onset. IgM Abs are transient and become undetectable after few weeks. As IgM titers decrease, another type, IgG Ab, starts forming around the time of resolution of symptoms, and the level in blood continues to rise for a period. Generally, IgG remains detectable in a person’s blood, and usually offers future immunity against the specific virus.
Detecting different Abs may help in differentiating those recently infected (by detecting IgM and possibly IgA) from those that have had the infection in the past (IgG).
These tests are part of the second phase of the epidemic, where, after molecular biology tests(PCR) performed to detect the specific presence of the virus, serological tests must be used to identify the presence of antibodies against COVID-19 in patients. In the immediate future, these tests will be used to precisely define the population immune to the disease (herd immunity). At a later stage, they will enable the identification of individuals who will require vaccination when it becomes available.
Snibe Co (China) has developed 2 tests for COVID-19, the SARS COV-2 IgG and IgM fully automated Chemiluminescent Immunoassay (CLIA) Tests. The test is typically quantitative and needs 1 – 2 hrs for result
The test is CE/IVD approved.
