Quantitative aspects of the latex-fixation and Whaaler-Rose tests.

The latex-fixation test (Singer and Plotz, 1956) is widely used as a serological criterion for rheumatoid arthritis (Alexander and McCarthy, 1966; Walton, 1968). The test is often carried out in serial dilution, by which a titre as well as an agglutination pattern is obtained. The usual practice is to choose a borderline titre in an empirical way and to call all titres above the borderline value positive and below it negative. Little attention has been paid in the literature to the possible significance of the titre value irrespective of this borderline. Population studies suggest that the presence and titre of rheumatoid factors may be related to the severity of rheumatoid disease (Valkenburg, Ball, Burch, Bennett, and Lawrence, 1966; den Oudsten, Planten, and Posthuma, 1968). Several authors (Jacobson, Kammerer, Wolf, Epstein, and Heller, 1956; Ball and Lawrence, 1963; Hill and Greenbury, 1965; Cats and Hazevoet, 1970) have demonstrated a close correlation between a positive haemagglutination or latex-fixation test and the presence of subcutaneous nodules, radiographic evidence of articular erosions, and stage of disease. There are, however, many examples in the literature of individual cases in which the titre values did not follow the course of the disease. The agglutination pattern has recently received some attention (Schubart, Cohen, and Calkins, 1964). It has been established that some sera contain thermolabile components which influence the titre and the agglutination pattern in the latex-fixation test. Thus, in serial dilutions of positive iheumatoid sera, agglutination may be absent in the initial tubes, resulting in a pattern which resembles the prozone of certain other antibody-antigen reactions. This phenomenon has been studied in our laboratory (Valkenburg and de Mos, 1958; Klein, 1964). The inhibitor is thermolabile and is probably identical to the first component of complement. Previous heat inactivation of serum abolishes the prozone phenomenon and may enhance agglutination. The presence of the inhibitor may conceal possible agglutinators of the rheumatoid factor type (Klein, Valkenburg, van Zwet, and Lafeber, 1966). The present study was undertaken to investigate whether titre values and prozone phenomena could provide additional data of interest for the clinical evaluation and biological significance of the latex fixation test. Some results obtained with the WaalerRose test are also discussed.