Assessment of serological markers associated with rheumatoid arthritis

Abstract

Progress in the detection and quantitation of autoantibodies associated with rheumatoid arthritis (RA) indicates an expanding role for serology in the diagnosis and predicting the prognosis of the disease. The advent of enzyme-linked immunoadsorbant assay (ELISA) methods for the quantitation of rheumatoid factor (RF) isotypes offers significant RA disease information substantially above that gained using traditional measurements of total RF. The ability to quantitate isotypes adds specificity for the diagnosis of RA and identifies those individuals that will tend to exhibit progressive, erosive disease. Other autoantibodies that are highly specific for RA recognize epitopes associated with proteins containing citrulline (e.g., antikeratin and antiperinuclear factor). A highly specific (92–98%) and relatively sensitive (∼80%) second-generation ELISA has been developed and marketed for the diagnosis of RA using cyclic citrullinated peptide as antigen (CCP). Population based studies indicate that finding multiple RF isotypes or antifilaggrin antibodies (synonymous with anti-CCP) in apparently normal individuals is highly predictive for the development of RA in subsequent years. More importantly, these markers are being recognized as indicative of disease course. Monitoring C-reactive protein and erythrocyte sedimentation rate continue to be a mainstay for determining RA disease activity, although acute-serum amyloid A may be a more sensitive marker for synovial inflammation.