When Does Arthralgia Progress to Rheumatoid Arthritis?

According to Wikipedia, autoantibodies are a type of protein produced by the immune system that are directed against one or more of the individual's own proteins.

This causes the immune system to attack normal cells within the body. This is the case for autoimmune disorders, to include rheumatoid arthritis.

Three types of the autoantibodies playing a role in the disease process of RA, that were utilized in the above-mentioned study, are:

• Anti-citrullinated protein antibody (ACPA): Citrulline is a natural by-product of the body's breakdown of an amino acid (the protein, arginine). With RA, the citrulline is often produced at a higher rate, triggers an immune response, and produces autoantibodies against healthy joint proteins. The test for ACPA can be used to diagnose RA. (Lab Tests Online)
• Rheumatoid factor (RF): Rheumatoid factor (RF) is an autoantibody produced by the body's immune system. This test detects and measures the amount of RF in your blood. It’s an indicator of inflammatory and autoimmune activity. About 80% of those with RA will have a positive RF test. (Lab Tests Online)
• Antibodies working against anti-carbamylated protein (anti-CarP): Anti-CarP is an autoantibody system uncovered in 2015 as being present in the blood of those with rheumatoid arthritis. Is also shown to be significantly increased in pre-symptomatic RA individuals. 

Levels of the above autoantibodies were used in the recent research study to determine the risk for those with ‘clinically suspect arthralgia’ for developing RA.

(For those with arthralgia being studied for their risk of developing RA, the research-participants are referred to as having ‘clinically suspect arthralgia’.)