To analyze indirect immunofluorescence (IIF) patterns and autoantibodies identified by line immunoassay (LIA) in rheumatoid arthritis (RA) patients, and to compare the autoantibody profiles with serological markers to determine their relevance.
A total of 153 specimens were obtained from RA patients for diagnostic or monitoring purposes. Erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), rheumatoid factor (RF), and anti-cyclic citrullinated peptide (anti-CCP) were measured, and autoantibody testing using IIF and LIA was performed. Frequencies of IIF patterns and autoantibodies identified by LIA were analyzed and compared with each other and with serologic markers of RF, including anti-CCP, ESR, and CRP.
The overall positivity of IIF and LIA results was 49.7% and 34.0%, respectively. The most frequent IIF pattern in RA was homogenous (20.9%), followed by dense fine speckled (DFS) pattern (17%). Anti-SS-A and/or anti-Ro-52 were most frequently detected in RA irrespective of the observed IIF pattern. Positive rates and intensities of autoantibodies detected did not differ by therapeutic regimen or disease activity, as reflected by CRP levels or ESR. Only anti-CCP showed a tendency to increase depending on IIF intensity.
RA patients did not display a specific or dominant IIF pattern or autoantibody presence, as identified by LIA. RA patients had lower frequencies of anti-SS-A and anti-Ro-52 compared with other systemic autoimmune diseases (serologically characteristic of RA). IIF and LIA appear insufficient for diagnosing RA and monitoring disease activity yet can be useful for screening and differentiating major systemic autoimmune diseases.