Gel diffusion tests, also known as precipitation tests or immunodiffusion tests, are laboratory techniques used to detect the presence or absence of specific antigens or antibodies in a biological sample. These tests are commonly employed in clinical and research settings to diagnose diseases, detect microbial infections, or evaluate immune responses.
The test involves the interaction of an antigen and antibody within a gel matrix. A gel medium, typically agarose or agar, is prepared with wells or troughs and loaded with antibodies or antigens. The sample to be tested, such as blood serum or other bodily fluid, is placed in a well adjacent to the antibodies or antigens. Over time, the molecules diffuse through the gel, resulting in the formation of visible precipitin lines or rings where the antigen-antibody complex forms.
Gel diffusion tests can be classified into different types based on the pattern of diffusion and precipitation observed. These include radial immunodiffusion (RID), in which antibodies are diffused radially from a central well; double immunodiffusion (Ouchterlony technique), where antigen and antibody wells are placed at a distance and interaction patterns are observed; and immunoelectrophoresis, combining gel electrophoresis with immunodiffusion.
These tests offer several advantages including simplicity, cost-effectiveness, and ability to screen multiple samples simultaneously. However, interpretation of results requires experience and careful observation, as factors like concentration, diffusion rates, and temperature can influence the final outcome. Gel diffusion tests are commonly used in various fields such as immunology, clinical microbiology, and serology, aiding in the detection and diagnosis of numerous diseases and infections.
