Detection and clinical significance of IgE rheumatoid factor

High serum IgE rheumatoid factor (RF) levels (greater than 100 ng/ml) were found using solid phase sandwich ELISA in 11 of 20 patients with rheumatoid arthritis having significant extraarticular symptoms (rheumatoid vasculitis) and only in 23 of 142 usual rheumatoid patients without such symptoms (p less than 0.01). A significant influence of other classes of RF and non-RF IgE on the ELISA for IgE RF was not observed in sera with levels of IgE RF over 50 ng/ml. The levels of IgE RF were not closely correlated with those of other classes of RF and total IgE. This study suggests that IgE RF might be one of the factors necessary to produce extraarticular rheumatoid vasculitis.