Profiling of rheumatoid arthritis associated autoantibodies.

An increasing number of rheumatoid arthritis (RA)-associated autoantibodies (AAB) are available for AAB profiling that may improve the early diagnosis of RA and provide prognostic and, probably theranostic information. To select AAB specificities for optimal AAB combinations, known AAB should be evaluated with standardized methods by means of standardized study designs and subjected to statistical analysis. Profiling of anti-citrullinated peptide/protein antibodies (ACPA), anti-A2/RA-33 antibodies, and rheumatoid factors (RF) IgM and IgA improves the serologic diagnosis of RA using cut-offs corresponding to 98% specificity for each parameter included. Currently, the combination of anti-CCP antibodies with RF IgM and RF IgA is recommended either in parallel or by stepwise determination. Because anti-CCP antibody demonstrated the best diagnostic performance for profiling, this AAB should be used for first-line screening. The main advantage of AAB profiling is the increased sensitivity for RA diagnosis. Additional benefits of AAB profiles comprise the increased diagnostic specificity of particular AAB combinations (e.g., ACPA plus RF or RF IgM plus RF IgA) and their possible association with disease development and/or therapy response. The inclusion of novel RA-associated AAB (RAAB) and use of clinically evaluated multiplex assays may facilitate the use of profiling in diagnostic routine laboratories.