Serologic testing is important in the workup and diagnosis of RA. Rheumatoid factor (RF) is present in 70%–80% of patients. However, it has limited specificity for the disease, as it can be positive in up to 10% of unaffected individuals and in about one-third of patients with systemic lupus erythematosus (SLE). Anti-CCP antibody is as sensitive as RF but has a higher specificity for RA (98%). Nevertheless, both of these tests may be negative in up to 50% of RA patients. Similarly, anti–mutated citrullinated vimentin (anti-MCV) antibody testing shows high specificity for the disease. Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) levels are usually elevated. Antinuclear antibody (ANA) testing is nonspecific, because only 30% of RA patients have positive results, but it can help exclude other diseases such as SLE. Although genetic testing is not performed routinely, the HLA-DRB1 gene appears to be the strongest known genetic risk factor for the development of RA.
Excerpted from BCSC 2020-2021 series: Section 1 - Update on General Medicine. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.