What is Rheumatoid Arthritis?
Rheumatoid Arthritis (RA) is a common autoimmune disease characterised by inflamation of the joints causing pain, swelling and stiffness. While it is more common in women over 40 years of age, it can affect anyone at any age, including children. The exact causes of RA are still unknown but the disease can be triggered by general illness and severe emotional or physical trauma. The disease also runs in families.
Why Test for Rheumatoid Arthritis?
With the availability of sophisticated therapies and drugs, it is important to diagnose and treat the disease early to avoid long- term damage.
How does the test work?
The CNS Rheumatoid Screen combines two key RA tests to provide the most accurate assessment; Rheumatoid Factors (RF) tests and Citrullinated Protein Antibodies (CPA) test.
RF are antibodies that are a common feature in RA. They have been found among IgM, IgA and IgG classes of immunoglobulinbut it is the IgM RF that shows a strong correlation with the onset of the disease.
The CNS IgM RF test uses ELISA technology and is calibrated against the first British Standard for Rheumatoid Factor. RF can be detected in up to 70% of RA patients, but is also detected in other autoimmune and infectious diseases, and in many healthy individuals.
Recently a new autoantibody was discovered which shows a high specificity for RA. The CPA test detects citrullinated filaggrin antibodies in serum. These are found almost exclusively in people with RA. It is a highly specific marker that is detected in 80% of RA patients, even in the early stages of the disease. The test uses the ELISA method and provides 99% specificity and up to 80% sensitivity.
- A positive CPA + RA IS 99.9% diagnostic of RA.
- CPA by itself is 90-95% certain and a positive result.
- RF by itself is about 55% certain.
Sample requirements and turnaround time.
A pin-prick bood sample is required. Results are available in 10 working days.