Elevation of only one rheumatoid factor isotype is not associated with increased prevalence of rheumatoid arthritis - a population based study

Objective: To analyse the relationship between different rheumatoid factor (RF) isotype patterns and the prevalence of RA. Methods: Serum samples, collected between 1973 and 1983 from nearly 14000 r andomly selected individuals, were screened for elevation of RF In 1987, 17 3 RF positive and 156 matched RF negative participants were evaluated clini cally. Results: Participants with elevation of only one RF isotype, most commonly IgM, did nor have significantly higher prevalence of RA than the RF negativ e controls. Of the 17 RF positive individuals who were diagnosed with RA, 1 4 (82%) had a combined elevation of IgM and Igh RF. Conclusion: In contrast to a combined elevation of IgM and IgA RF, elevatio n of only one RF isotype may not be a significant risk factor for the devel opment of RA.