AGBL2 and synovial sarcoma: However, the diagnostic sensitivity of anti-CCP antibodies decrease to 70% in very early RA, and there is a relatively high frequency of anti-CCP2 antibodies in patients with non-RA connective tissue disorders, such as SLE (15%), SS (14%), polymyositis/dermatomyositis (23%) and scleroderma (16%) [61].