[The clinical and prognostic importance of IgM rheumatoid factors]

On a total of 1000 subjects diagnosed as having rheumatoid arthritis it was possible to positively correlate the proportion of seropositivity of IgM rheumatoid factors and/or higher titer values to the following clinical characteristics: Male sex; existence, severity, and symmetry of articular alterations determined by morphological x-ray examinations; unfavorable functional values; high inflammatory activity; involvement of various organs; and high rate of progress. So far as this particular clinical picture is concerned, the detection of rheumatoid factors must, therefore, be considered unfavorable to a prediction or conclusion regarding the course of disease, whereas seronegative forms may be regarded as relatively benign.