title: Rheumatoid factor: a cause of fals positive histoplasmin latex agglutination.
abstract: Ten of thirteen patients with positive histolatex agglutination titers of 1:32 or greater had no evidence of acute histoplasmosis. Three of these false positives had rheumatoid arthritis. A fourth had a rising mycoplasma complement fixation titer, and the fifth had a high titer of cold agglutinins. All of these are associated with abnormal immunoglobulin M production. To evaluate the role of rheumatoid factor in producing false positive histolatex agglutination, the histolatex test was performed on sera from 32 patients having rheumatoid factor at a titer of 1:40 or greater. Four of these sera agglutinated the histoplasmin-coated latex particles at titers of 1:32 or greater. Review of clinical records suggests the this reactivity is nonspecific. It is our purpose to call attention to rheumatoic factor as a cause of false positive histolatex agglutination.
mesh_terms: D005189:False Positive Reactions; D006659:Histoplasmin; D006660:Histoplasmosis / Q000175:diagnosis; D006801:Humans; D007841:Latex Fixation Tests; D012217:Rheumatoid Factor / Q000494:pharmacology*
chemical_list: D006659:Histoplasmin; D012217:Rheumatoid Factor