Diagnostic Use
Rheumatoid Arthritis (RA) is one of the most common systemic autoimmune diseases. The aetiology of the disease is unknown. Approximately 0.5% of the world population is affected, and twice as many women as men get the disease. Until recently, the only serological test routinely used was the determination of the presence of rheumatoid factors (RF) in serum. RF are antibodies directed to the Fc region of immunoglobulins of the IgG class. RF can be of the IgM, IgG and IgA immunoglobulin classes. The presence of IgM RF is a hallmark of RA, found in approximately 50-90% of these patients. However, IgM RF are found in people with infections, other autoimmune disease, and some healthy individuals. IgG RF are less sensitive but more specific for RA than IgM RF.
It is important for disease management to diagnose and treat people with RA as early possible. It has been known for many years that anti-perinuclear autoantibodies, also called anti-keratin, are found in people with RA. Recently it was discovered that these autoantibodies recognise an epitope that contains the deimidated form of arginine called cirulline. A circular peptide containing citrulline called CCP (Cyclic Citrullinated Peptide) was found to be better at discriminating RA patients than either the perinuclear autoantibody test or the test for rheumatoid factor. Additionally, RA patients with anti-CCP may progress to a more severe disease than those who do not have anti-CCP. In published literature, approximately 70% of patients with RA are positive for anti-CCP, while only about 2% of healthy blood donors and disease control subjects are positive. Thus, both negative and positive results on this test have high predictive values. A recent study found citrullinated proteins in the joints of patients with RA, but not in joints form health volunteers. These results lend a theoretical basis for the presence of anti-CCP in RA patients and a possible pathogenic role for these antibodies.
Reference Intervals
Abnormal – Units: Units
| Age Range |
Either Sex |
| All |
>= 20 [1] |
[1] Levels of CCP antibodies in this interval are considered positive.
Test Method
ELISA - automated
DS2 robotic processing
Limitations / Interference
Grossly haemolysed and/or high lipaemic serum specimens.
The presence of immune complexes or other immunoglobulin aggregates in the patient sample may cause an increased level of non-specific binding and produce false positives in this assay.
Not all RA patients are positive for CCP antibodies.
Results of this assay should be used in conjunction with clinical findings and other serological tests.
This assay performance characteristics have not been established for matrices other than serum.