Non-specific inflammation
Factors allowing an abnormal immune response, once initiated, become permanent and chronic. These factors are genetic disorders which change regulation of the adaptive immune response. Genetic factors interact with environmental risk factors for RA, with cigarette smoking as the most clearly defined risk factor.Other environmental and hormonal factors may explain higher risks for women, including onset after childbirth and hormonal medications. A possibility for increased susceptibility is that negative feedback mechanisms – which normally maintain tolerance – are overtaken by positive feedback mechanisms for certain antigens, such as IgG Fc bound by rheumatoid factor and citrullinated fibrinogen bound by antibodies to citrullinated peptides (ACPA - Anti–citrullinated protein antibody). A debate on the relative roles of B-cell produced immune complexes and T cell products in inflammation in RA has continued for 30 years, but neither cell is necessary at the site of inflammation, only autoantibodies to IgGFc, known as rheumatoid factors and ACPA, with ACPA having an 80% specificity for diagnosing RA. As with other autoimmune diseases, people with RA have abnormally glycosylated antibodies, which are believed to promote joint inflammation. Amplification in the synovium
Once the generalized abnormal immune response has become established – which may take several years before any symptoms occur – plasma cells derived from B lymphocytes produce rheumatoid factors and ACPA of the IgG and IgM classes in large quantities. These activate macrophages through Fc receptor and complement binding, which is part of the intense inflammation in RA.
In 2008 a serological point-of-care test for the early detection of RA  combined the detection of RF and anti-MCV with a sensitivity of 72% and specificity of 99.7%.To improve the diagnostic capture rate in the early detection of patients with RA and to risk stratify these individuals, the rheumatology field continues to seek complementary markers to both RF and anti-CCP. 14-3-3η (YWHAH) is one such marker that complements RF and anti-CCP, along with other serological measures like c-reactive protein. In a systematic review, 14-3-3η has been described as a welcome addition to the rheumatology field. The authors indicate that the serum based 14-3-η marker is additive to the armamentarium of existing tools available to clinicians, and that there is adequate clinical evidence to support its clinical benefits.Other blood tests are usually done to differentiate from other causes of arthritis, like the erythrocyte sedimentation rate (ESR), C-reactive protein, full blood count, kidney function, liver enzymes and other immunological tests (e.g., antinuclear antibody/ANA) are all performed at this stage. Elevated ferritin levels can reveal hemochromatosis, a mimic of RA, or be a sign of Stills disease, a seronegative, usually juvenile, variant of rheumatoid arthritis. Classification criteria
In 2010, the 2010 ACR / EULAR Rheumatoid Arthritis Classification Criteria were introduced.The new criteria are not diagnostic criteria, but are classification criteria to identify disease with a high likelihood of developing a chronic form.