FII haemagglutination test for serum antigammaglobulin factors in arthritides sero-positive and sero-negative by other tests.

The serological tests for rheumatoid serum factors fall into two categories, in which rabbit antibody and human gamma globulin respectively provide the reactant. Clinically, the chief use of these tests for serum antiglobulin factors is to assist diagnosis of rheumatoid arthritis, and serum titres above given levels are commonly regarded as "positive". In most tests the "positive" level has been selected to include as many rheumatoid arthritic subjects as possible, but at the same time to exclude most nonrheumatoid subjects. Nevertheless it is well-known that a proportion of cases of undoubted rheumatoid arthritis assessed in this way are "sero-negative"; and in juvenile chronic polyarthritis (Still's disease) especially this sero-negative proportion is large. The question therefore arises whether quantitative measurement by a sensitive method might reveal the presence of rheumatoid antiglobulin serum factors in "sero-negative" patients. The FII haemagglutination test originally devised by Heller, Jacobson, Kolodny, and Kammerer (1954) appears to provide such a method. This test detects antiglobulin antibody in patients' sera by haemagglutination of tannic acid treated sheep red cells coated with Cohn Fraction II gamma globulin prepared from human serum. Jacobson, Kammerer, Wolf, Epstein, and Heller (1956) used this method to test sera from a large group of patients with rheumatoid arthritis and other arthritides, and from non-rheumatic patients, and compared results with those obtained by a haemagglutination test using sheep cells sensitized with rabbit anti-sheep antibody. In the FIT test they accepted as positive titres of 1: 28 or more, and in the sensitized sheep cell test 4-fold enhancement or more of the agglutination titre when sheep serum diluent was used instead of saline. They found good agreement between the two tests when positivity was defined in this way. Others have reported that the FII test is considerably more sensitive than the latex or differential agglutination test for rheumatoid factor (Peltier and Christian, 1959; Oreskes and Siltzbach, 1968; Oreskes, Rosenblatt, Spiera, and Meadows, 1968). This paper presents results obtained with the FII test on sera from healthy subjects and from patients with arthritis or other diseases; the sera were also tested by two other methods-the differential agglutination test and latex particle agglutination, representing rabbit and human reactants respectively. In particular, the investigation sought to establish whether the FII test could detect serum antigammaglobulin factors in conditions usually regarded as sero-negative.