A study of rheumatoid factors in juvenile rheumatoid arthritis (chronic polyarthritis) by the photometric latex test.

The photometric latex test (PLT) for the detection of rheumatoid factors (RF), developed and clinically evaluated in adult rheumatoid arthritis, was applied in a study of juvenile rheumatoid arthritis (JRA). A total of 40 individuals with JRA, 27 with other collagen diseases and 24 in a control group were examined. The incidence of seropositives by PLT was 50% in JRA, 33% in collagen diseases and 17% in controls. The percentage of JRA was significantly higher than in the controls, and also higher than values in the literature claiming that only about 20% of JRA patients are seropositive. These findings were discussed concerning the diagnostic capability of PLT as compared with other serologic tests for RF. The increase in PLT titer values was found to indicate an aggravation of the inflammatory process and could help estimate the clinical stage of the disease. A follow-up of patient titer values could be of great diagnostic value. The data on serum immunoglobulins and complement fractions levels could not confirm the findings on a significant increase in JRA patients, but following of "level profiles" of each patient could add to the estimation of patient's clinical status. In cases of seropositives when other laboratory parameters did not indicate a clear transition from the chronic active to acute stage of disease, the only parameter which often showed such a transition is the RF titer determined by PLT testing, which could be of importance for a timely change of the therapy.