[citation needed] Agglutination tests, specific to a variety of pathogens, can be designed and manufactured for clinicians by coating microbeads of latex with pathogen-specific antigens or antibodies.
In performing a test, laboratory clinicians will mix a patient's cerebrospinal fluid, serum or urine with the coated latex particles in serial dilutions with normal saline (important to avoid the prozone effect) and observe for agglutination (clumping).
Agglutination of the beads in any of the dilutions is considered a positive result, confirming either that the patient's body has produced the pathogen-specific antibody (if the test supplied the antigen) or that the specimen contains the pathogen's antigen (if the test supplied the antibody).
For example, assays exist for rubella virus, rotavirus, and rheumatoid factor, and an excellent LA test is available for cryptococcus.
[1] Agglutination techniques are also used in definitive diagnosis of group A streptococcal infection.