A Serology (antibody) test looks for the presence of isotype antibodies, which are specific proteins (IgG, IgM, IgA) made in response to infections. These antibodies would be detected in the blood of people who have been tested, and are currently or previously infected. Identifying the antibodies indicates there has been a response to the infection which is especially important for detecting previous infections in people who had few or no symptoms (asymptomatic).