Rheumatoid Factor (RF) is an immunoglibulin M protein, Produced by body's own immune system. Being an autoantibody by nature it attacks bodies on tissues as it mistakenly identified them as foreign entry. RF is one of the factors associated with diagnosis of rheumatoid arthritis (RA) and is also essential for differentiating it from other rheumatic diseases. The higher concentration of RF in serum indicates the severity of the disease however there are some rare types of rheumatoid arthritis for which RF show seronegativity negativity. Serum level of RF can be positive in other non RA conditions such as hepatitis viral or parasitic infections and other auto immune disease there is a progressive increase in RF levels with age
