Tehran University of Medical Sciences Iranian Journal of Public Health 2251-6085 16 1-4 1987 06 15 101 110 F. Zaini A.S.A. Mehbod 2015 10 03 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. https://ijph.tums.ac.ir/index.php/ijph/article/view/2747 https://ijph.tums.ac.ir/index.php/ijph/article/download/2747/2727