The ability of rheumatoid serum to cause nonspecific agglutination of fine particulate matter was first noted by Cecil in 1930,1 who studied the effects of rheumatoid sera on certain strains of streptococci. Since that time many tests for rheumatoid arthritis, which are dependent on that phenomenon, have been developed.2 The responsible serum factor is absent or present in minimal amounts in serums of normal subjects. The positive agglutination tests are believed to result from an interaction between the "rheumatoid factor" and a "reactant" such as sheep cells, certain streptococci, or Cohn-Fraction-II-coated bentonite or latex particles.2 It is believed that the various particles utilized must be coated by this "sensitizing factor" or "reactant," which is present in the γ-globulin or Cohn Fraction II.
The original latex-fixation test (FII L.P.), developed by Plotz and Singer,3 was positive in 71% of patients with rheumatoid arthritis, but a later modification,
REED WB, HEISKELL CL, BECKER SW. Negative Latex-Fixation Test in Psoriatic Arthritis. Arch Dermatol. 1961;83(4):653–656. doi:10.1001/archderm.1961.01580100117016
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