Is Anti Cyclic citrullinated peptide a useful laboratory test for the diagnosis of rheumatoid arthritis?

Aim of the Study: To evaluate Anti Cyclic citrullinated peptide (anti-CCP) and Rheumatoid Factor (RF) sensitivity and specificity in patients with Rheumatoid Arthritis (RA).
Materials and Methods: Anti-CCP and RAtest for the assessment of RF have been tried out in 35 patients with RA and in a group of 42 patients whose hands were affected by arthralgic/arthritis-like symptoms.
Results: Sensitivity of anti-CCP was 71,4% with 95,2% of specificity. RAtest sensitivity was 91,4% with specificity of 31%. Anti-CCP and RAtest both positive showed an overall 71.4% sensitivity and 95.2% specificity; sensitivity was 91.4% and specificity was 31.0%, if at least RAtest or anti-CCP resulted positive, The positive predictive value of the two test performed together was 97.0%, higher than that of anti-CCP (71.4%) and RAtest (88.5%9) alone. The negative predictive value of the two test performed together was 30.9% similar to that of the RAtest performed alone (30.9%). All patients affected by HCV related chronic liver disease were negative for anti-CCP test; 12/14 of them had RAtest positive.
Conclusions: Anti-CCP antibody has a diagnostic specificity higher than RF. Anti-CCP and RA tests together prove to have the some specificity as anti-CCP alone and a lower sensitivity. Sensitivity is better when at least either RAtest or anti-CCP results positive. The best positive predictive value is obtained performing both anti-CCP and RAtest. Anti-CCP is a useful laboratory marker to confirm the diagnosis of rheumatoid arthritis; it seems to be very important to differentiate patients with RA from those with HCV related arthritis.