A latex fixation test is an agglutination

Agglutination (biology)

Agglutination is the clumping of particles. The word agglutination comes from the Latin agglutinare, meaning "to glue."This occurs in biology in three main examples:...

 technique used to detect antibodies, such as those produced in response to the rubella virus

Rubella virus

Rubella virus is the pathogenic agent of the disease Rubella, and is the cause of congenital rubella syndrome when infection occurs during the first weeks of lunacy.Humans are the only known host of this virus....

 or the rheumatoid factor

Rheumatoid factor

Rheumatoid factor is an autoantibody most relevant in rheumatoid arthritis. It is defined as an antibody against the Fc portion of IgG. RF and IgG join to form immune complexes that contribute to the disease process...

. May be used for Rickettsia, coccidioidomycosis, though numerous sources of interferences (e.g., large immune complexes and high protein concentrations) lessen the utility of the latex agglutination (LA) test in most situations. There is an excellent LA test for cryptococcus. It also is used in definitive diagnosis of Group A streptococcus.

In a latex fixation test, a sample is mixed with latex beads coated with antibodies. If the antigen is present, it will react with the antibodies causing the latex beads to clump.http://www.umm.edu/ency/article/003334.htm