Rheumatoid factors, anti-filaggrin antibodies and low in vitro interleukin-2 and interferon-gamma production are useful immunological markers for early diagnosis of community cases of rheumatoid arthritis. A preliminary study.

OBJECTIVE: To determine whether measurements of different autoantibodies (Ab) and cytokines are useful to distinguish very early rheumatoid arthritis (RA) from other inflammatory rheumatisms.
METHODS: From a population-based recruitment, 32 patients with very early polyarthritis (median duration: 4 months) were studied. Evaluations at entry (M0), and at 6 (M6) and 12 months (M12). Ab tested: rheumatoid factors (RF) by agglutination methods and ELISA, antiperinuclear factor (APF), antikeratin Ab (AKA), anti-Sa and antinuclear Ab. Cytokine production (TNFalpha, IL2, IFNgamma, IL1beta, IL10) in whole blood cell culture (WBCC) was determined at M0. At M12, patients were classified as having RA (N = 15) or other rheumatic diseases.
RESULTS: At M0, AKA/APF and anti-Sa Ab frequencies were low, 13% and 7%, respectively. While most Ab detected at M0 persisted, others appeared during follow-up, particularly APF, which rose from 13 to 40% at M12. At M6, IgM-RF was detected in two RA patients exclusively by ELISA. AKA/APF were found to be highly specific markers for RA (100% specificity). At some time during follow-up, two RF-negative RA patients were AKA-positive. In two patients, AKA and APF were present at M0 before they satisfied ACR criteria. IL2 and IFNgamma production was significantly lower (P < 0.05) for RA patients.
CONCLUSION: AKA/APF and anti-Sa Ab were detected in community cases of very early RA. AKA/APF and RF detected by ELISA might contribute to an earlier diagnosis of RA. Low production of IFNgamma and IL2 in WBCC constituted a distinct immunopathological feature in very early RA patients.