Serological Testing

Serological tests are diagnostic methods that are used to identify antibodies and antigens in a patient’s samples. Serological tests may be performed to diagnose infections and autoimmune illnesses, to check if a person has immunity to certain diseases, and in many other situations, such as determining an individual’s blood type.

Several methods can be used to detect antibodies and antigens, including ELISA, agglutination, precipitation, complement-fixation, fluorescent antibodies and more recently chemiluminescence. Serological testing features prominently in Covid-19 testing.

It is used to test a patients sample for the presence of antibodies to the SARS nCoV2 virus that causes Covid-19. The presence of these antibodies tells us that the patient was infected with the virus. The test cannot be used to determine if you are currently or newly infected, that requires a NAAT based test that searches for actual viral material rather than antibodies and antigens

What do we use Serological Testing for?

Blood typing is typically performed using serologic methods. The antigens on a person’s red blood cells, which determine their blood type, are identified using reagents that contain antibodies, called antisera. When the antibodies bind to red blood cells that express the corresponding antigen, they cause red blood cells to clump together (agglutinate). These clumps can then be identified visually.

Serologic tests also play a key role in transfusion medicine. Prior to a blood transfusion,the test is used for crossmatching, a process that ensures a donor and recipient are compatible. The direct antiglobulin test is performed to detect if antibodies are bound to red blood cells inside the person’s body, which is abnormal and can occur in conditions like autoimmune hemolytic anemia, hemolytic disease of the newborn and transfusion reactions.

In Immunology, Serologic tests can help to diagnose autoimmune disorders by identifying abnormal antibodies directed against a person’s own tissues.

The importance of Serology

Serological surveys are often used by epidemiologists to determine the prevalence of a disease in a population. Such surveys are sometimes performed by random, anonymous sampling from samples taken for other medical tests or to assess the prevalence of antibodies of a specific organism or protective titre of antibodies in a population.

These surveys are potentially the most direct and informative technique available to infer the dynamics of a population’s susceptibility and level of immunity. The emergence of the tests usefulness in tracking viral outbreaks and measuring prevalence in communities across the globe has been made evident by the Coronavirus Pandemic of 2019/20