The Diagnostic Value of Anti-Cyclic Citrullinated Peptide Antibodies, Adenosine Deaminase Activity and Other Potential Biomarkers for Predicting and Monitoring Rheumatoid Arthritis The aim of this study was to investigate the presence of anti-cyclic citrullinated peptide antibodies (anti-CCP2) in RA and non-RA patients and to evaluate the combination of these auto-antibodies with some other markers such as RF and CRP. We examined the enzymatic activity of ADA in RA patients without therapy and RA patients treated with methotrexate. Therefore, the aim of this study was also to assess the possibility of introducing these biochemical parameters in the diagnosis and monitoring of the RA patients in this region. Serum antibodies directed to cyclic citrullinated peptide were analyzed using an anti-CCP2 antibody ELISA. Serum ADA activity was measured by a spectrophotometer using adenosine as substrate (Giusti method). Rheumatoid factor (IgG-RF) was analyzed using a latex agglutination test. Serum CRP was measured by an immunoturbidimetric assay. The measurement of anti-CCP2 by itself, is useful for the diagnosis of RA for its high sensitivity and specificity, however, a combined use of anti-CCP2 with RF is much more useful. Serum ADA activity can be used as a biochemical marker of inflammation in RA. Measuring CRP in the RA patients has no diagnostic value.