A latex agglutination test is a rapid immunoassay that uses polystyrene latex particles coated with specific antibodies or antigens. When mixed with a sample containing the corresponding target, the particles clump together, producing a visible agglutination reaction.
Principle and Laboratory Use
In latex agglutination, antibodies or antigens are adsorbed onto microscopic latex beads to enhance visibility. When a patient specimen or isolate is added, the coated particles crosslink with the complementary antigen or antibody, forming a lattice that becomes visible to the naked eye. The test can be qualitative or semi-quantitative depending on dilution series. Because the reaction occurs quickly without the need for complex equipment, latex agglutination is useful in clinical laboratories for screening and identification. Sensitivity depends on the density of epitopes and the affinity of the reagent antibodies. Non-specific binding can occur if samples contain proteins that adhere to latex surfaces, and a prozone effect can lead to false negatives at high antigen concentrations, so proper sample dilution and controls are important.
Examples in Diagnostics
Latex agglutination has been applied to many organisms and analytes. For bacterial identification, commercial kits detect clumping factor and protein A to distinguish Staphylococcus aureus from coagulase-negative staphylococci. Slide agglutination kits use latex beads coated with group-specific antibodies to assign Lancefield groups to β‑hemolytic streptococci. Antigen detection assays test cerebrospinal fluid or serum for capsular polysaccharides of Cryptococcus neoformans, Haemophilus influenzae type b, Neisseria meningitidis and Streptococcus pneumoniae in cases of meningitis. Latex agglutination is also used to detect rheumatoid factor, an autoantibody that binds the Fc region of IgG, and to detect viral antigens such as rotavirus in stool. These tests provide rapid results but are often supplemented by culture, molecular methods or other serologic assays for confirmation. A latex agglutination test offers a simple, low-cost means of detecting antigens or antibodies in a variety of clinical and industrial settings. Its speed and ease of interpretation make it a valuable screening tool, although confirmatory testing is often required to ensure accuracy. Related Terms: Agglutination, Serology, Antigen detection, Slide agglutination, Coagulase test