Serological testing is a laboratory method used to detect and measure the presence of antibodies or antigens in a sample, usually blood. This type of testing helps diagnose infections, autoimmune diseases, and allergies by identifying the immune response to specific pathogens, such as viruses or bacteria. The results of serological tests can provide valuable information about a person's immune status or exposure to certain diseases, such as HIV, Hepatitis, or COVID-19. These tests are often used in conjunction with other diagnostic methods to give a comprehensive view of a patient's health.