ABSTRACT
To assess the value of the second test generation A-CCP2 compared with rheumatoid factor isotypes [IgG-RF and IgM-RF] in RA patients. Also to test the additional diagnostic value of combined measurement of both A-CCP2 and RF, and to clarify the relation between anti-CCP2 and disease activity, disease duration and joint destruction. Ninety RA patients, 40 patients with other different connective tissue diseases or vasculitis and 50 healthy normal controls were included in the study. After thorough history, clinical assessment of RA was done. Erythrocyte sedimentation rate [ESR] and C-reactive protein [CRP], as laboratory parameters of disease activity were measured. Radiological evaluation was done. Then RF isotypes [both IgG and IgM] and A-CCP2 were assessed. A-CCP2 was less sensitive than RF [sensitivity = 60.0% vs. 80.0% respectively], but A-CCP2 showed a better specificity than RF [96.0% in A-CCP2 vs. 92.0% in RF]. Best sensitivity [88.9%], specificity [98.0%] and test accuracy [90.7%] were recorded in combined RF and A-CCP2 measurement. A-CCP2 could detect 44.4% more cases of RA that were negative when tested with RF, 25% were early within 1 year. There is significant association between A-CCP2 positivity and increased score of disease activity, either clinically [X[2]=9.0, p<0.05] or laboratory wise [t=11.4, p<0.001 for ESR and t=18.9, p<0.001 for CRP]. Also showed more frequent positivity with increased score of X-ray grading [X[2]=8.35, p<0.05], but no relation with disease duration [t=1.6, p>0.05]. A-CCP2 has a higher specificity and RF has a higher sensitivity. Best sensitivity, specificity and accuracy were recorded in combined RF and A-CCP2 measurement. The additional diagnostic value of A-CCP2 is even more impressive in the early course of disease, in patients with severe joint destruction, and in patients with very active disease. Its presence is indicative for poorer radiological outcome. We recommend adding A-CCP2 measurement to the routinely used RF tests