the puzzle of the false positve reactions in cr. neoformanse’s capsular antigen slide lates agglutination test by sera of patients with rheumatoid arthritis

different examination have shown that rheumatoid factor is not responsible for false positive reaction (f.p.r.) in cr. neoformanse’s free capsular antigen latex agglutination test, whereas high levels of iron in sera of patients with rheumatoid arthritis as well as other sera was responsible not only for this f.p.r. , but also had an important role in the production of f.p.r. in many slide latex agglutination tests. this is because of iron’s ion reaction with reagent’s preservative: sodium azid and/or negative charge of the antigens fixed to the latex particles.