Ccp-ak

antibodies against cyclic citrullinated peptide. A highly specific marker for rheumatoid arthritis.

Up to 80 % of patients with rheumatoid arthritis (RA) show IgG class autoantibodies against the epidermal protein filaggrin in serum. Filaggrins are proteins that bind keratin filaments together. The amino acid citrulline is an important component of the binding epitopes for CCP-AK. CCP-AK can be detected very early in the course of the disease and have a high prognostic value: Compared to the rheumatoid factor, antibodies against CCP have a significantly higher specificity (CCP-AK: 80%, RF: 79%) with the same sensitivity (CCP-AK: 96%, RF: 63%). 10-15% of patients with psoriatic arthritis have CCP-AK (mostly IgG-AK, less often IgM-AK). These are absent in psoriatic patients without arthritis. The prevalence is < 1% in collagenoses such as SLE, Sjögren's syndrome or dermatomyositis/polymyositis.