Rheumatoid arthritis (RA) is a common autoimmune disease estimated to affect roughly one percent of the global population. Approximately 80 percent of people diagnosed with RA will suffer from synovitis (inflammation of the soft synovial joint tissue), cartilage damage and develop bony erosions within one year of diagnosis. Rheumatoid arthritis causes significant loss in work productivity, with up to one-third of those diagnosed unable to work within two years of the onset of RA.
Traditional methods of diagnosing RA rely both on a physical examination and on blood markers that differentiate RA from other autoimmune connective tissue diseases. Research into new blood markers shows promise in providing additional blood tests to help diagnose RA earlier, before symptoms appear; those diagnosed earlier could then be started on drug therapies designed to halt or slow down debilitating disease effects.
The five most common blood markers used to diagnose rheumatoid arthritis
1.Erythrocyte sedimentation rate (ESR)
The ESR measures general inflammation, and is not specific for RA. It measures the rate at which red cells settle in one hour. The higher the value, the higher the level of inflammation.
2. C-Reactive protein (CRP)
This blood test also measures the presence and level of inflammation in the body. It, too, is not specific for RA. CRP is a protein produced by the liver that becomes elevated with inflammation.
3.Rheumatoid Factor (RF)
The rheumatoid factor is an auto-antibody directed against the Fc portion of immunoglobulin found in the blood of about 80 percent of people with rheumatoid arthritis. This is the most common blood test used in diagnosing RA. However, up to 30 percent of those with RA won’t have a positive RF, and it may not be present early in the course of the disease. Other diseases also may show elevated RF levels.
4.Anti-cyclic citrullinated peptide antibody (anti-CCP)
Citrullination is a normal process that can go awry when specific enzymes and proteins leak out of dying cells and contact the immune system, leading to the production of autoantibodies, i.e. anti-CCPs. This is a newer blood marker that has begun to be widely used to diagnose RA, especially in combination with RF. CCP antibodies are rarely seen in patients who don’t have RA, and so this test was incorporated into the American College of Rheumatology’s revised 2010 criteria for diagnosis of RA.
5. Protein biomarker 14-3-3eta
In April, 2013, Quest Diagnostics introduced a new blood test for RA based on a protein biomarker known as 14-3-3. According to the company, this test outperformed both RF and anti-CCP blood tests in identifying early cases of RA. The company maintains that early RA treatment can benefit patients, but that such benefit accrues from earlier diagnosis, which has been “elusive, in part due to absence of precise blood tests.”
Potential new biomarkers for diagnosis of rheumatoid arthritis
A study conducted by Swedish researchers compared donated blood samples before onset of RA symptoms (pre-patient) and after onset with matched control subjects. The plasma levels of 30 cytokines and other markers were measured. Cytokines are a group of proteins that can promote or reduce inflammation. Researchers concluded that those people who later developed RA had “significantly increased levels of several cytokines, cytokine-related factors and chemokines representing the adaptive immune system (Th1, Th2, and Treg cell-related factors).” This study and others like it may help point the way toward development of additional RA-specific blood tests and ultimately, drug therapies based on novel biomarkers.
We can help you locate the right type of biospecimen for critical immune-disease research. How can we help source your RA samples?