Rheumatoid Factor (RF) ( 1 )
Rheumatoid factor (Rf) is an immunoglobulin M protein, produced by body’s own immune system. Being an autoantibody by nature, it attacks body’s own tissues as it mistakenly identifies them as foreign entity. RF is one of the factors associated with diagnosis of rheumatoid arthritis (RA) and is also essential fix differentiating it from other rheumatic diseases. The higher concentration of RT in serum indicates the severity of the disease. However, there are some rare types of rheumatoid arthritis fix which RF show seronegativity. Serum level of RF can be positive in other non-RA conditions such as hepatitis, viral or parasitic infections, endocarditis and other autoimmune diseases. There is a progressive increase in RF levels with age.