Citrullinated peptide is a protein of the body. When the immune system is disturbed, this protein begins to be "attacked" by its own defenses - antibodies. That is, the detection of these antibodies to cyclic citrullinated peptide indicates the presence of autoimmune diseases in the patient - rheumatoid arthritis or systemic lupus erythematosis.

Rheumatoid arthritis is a severe autoimmune disease that manifests with symmetrical arthritis (both small and large joints) 
A characteristic sign is a feeling of stiffness in the morning lasting more than one hour. Joints begin to ache, deform, become swollen.

The test has a number of advantages over rheumatoid factor (see rheumatoid factor), which is also used to diagnose these diseases:

• - marked specifity (there are no other factors that can lead to the appearance of the AB-CCP in the blood);
• - appearance at the very beginning of the disease before clinical manifestations;
• - positive result even in the seronegative variant of rheumatoid arthritis (such patients have a negative result of the rheumatoid factor test);
• - AB-CCP concentration makes it possible to assess the prognosis and severity of the disease.