CLASS-SPECIFIC RHEUMATOID FACTORS IN JUVENILE CHRONIC ARTHRITIS. CLINICAL ASSOCIATIONS

Abstract

The study aimed at determining the prevalence of the class-specific rheumatoid factors (RFs) in juvenile chronic arthritis (JCA) and evaluating the diagnostic test qualities. A total of JCA 79 patients (48 with pauciarticular form, 17 of whom with extending pauciarthritis), 31 with polyarticular for, as well as 125 control children (58 healthy and 67 disease controls) were tested. Most JCA patients (95%) had negative Waaler-Rose test. ELISAfor the detection of IgM-, IgA- and IgG- isotypes of RFs was used. The diagnostic characteristics of the tests were evaluated by clinico-epidemiological methods (assessment of sensitivity, specificity, positive predictive value, and likelihood ratio). The prevalence of IgG-, IgA- and IgM-RF in JCA versus all controls at optimal cut offtitres was 16 %, 22 c/c and 32%, respectively. The test for IgG-RF was not diagnostically significant. IgA-RF had the highest prevalence in the polyarticular form (40 %). The diagnostic qualities of the test were significant, mostly concerning the differentiation of the polyarticular course of JCA and the presence of erosive arthritis. IgM-RF was most typical of the polyarticular form (55 %) followed by the extending pauciarthritis (41 %). The diagnostic test qualities were significant and most prominent to distinguish the polyarticular course and erosive arthritis. IgM- and IgA-RFs had significant diagnostic value in JCA, mainly for the polyarticular and extending pauciarticular form and also in regard to more severe disease course. IgGRF had no diagnostic significance for JCA.