This is important, since in the early stages of RA, the synovium is primarily affected, and synovitis seems to be the best predictive marker of future joint damage. Blood tests
When RA is clinically suspected, a physician may test for rheumatoid factor (RF) and anti-citrullinated protein antibodies (ACPAs measured as anti-CCP antibodies). It is positive in 75–85%, but a  negative RF or CCP antibody does not rule out RA, rather, the arthritis is called seronegative, which is in about 15–25% of people with RA. During the first year of illness, rheumatoid factor is more likely to be negative with some individuals becoming seropositive over time. RF is a non-specific antibody and seen in about 10% of healthy people, in many other chronic infections like hepatitis C, and chronic autoimmune diseases such as Sjögrens syndrome and systemic lupus erythematosus. Therefore, the test is not specific for RA.Hence, new serological tests check for anti-citrullinated protein antibodies ACPAs. These tests are again positive in 61–75% of all RA cases, but with a specificity of around 95%. As with RF, ACPAs are many times present before symptoms have started.The by far most common clinical test for ACPAs is the anti-cyclic citrullinated peptide (anti CCP) ELISA.
More general osteoporosis is probably contributed to by immobility, systemic cytokine effects, local cytokine release in bone marrow and corticosteroid therapy. Cancer
The incidence of lymphoma is increased, although it is uncommon and associated with the chronic inflammation, not the treatment of RA. The risk of non-melanoma skin cancer is increased in people with RA compared to the general population, an association possibly due to the use of immunosuppression agents for treating RA. Teeth
Periodontitis and tooth loss are common in people with rheumatoid arthritis. Risk factors
RA is a systemic (whole body) autoimmune disease. Some genetic and environmental factors affect the risk for RA. Genetic
Worldwide, RA affects approximately 1% of the adult population and occurs one in 1000 children. Studies show RA primarily affects individuals between the ages of 40–60 years and is seen more commonly in females. A family history of RA increases the risk around three to five times; as of 2016, it was estimated that genetics may account for between 40 and 65% of cases of seropositive RA, but only around 20% for seronegative RA. RA is strongly associated with genes of the inherited tissue type major histocompatibility complex (MHC) antigen. HLA-DR4 is the major genetic factor implicated – the relative importance varies across ethnic groups.Genome-wide association studies examining single-nucleotide polymorphisms have found around one hundred alleles associated with RA risk. Risk alleles within the HLA (particularly HLA-DRB1) genes harbor more risk than other loci. The HLA encodes proteins which controls recognition of self versus nonself molecules.