Quantitative Rheumatoid Factor Test - Quantitative Rheumatoid Factor (RF) Test

This quantitative immunoassay measures the concentration of IgM autoantibodies directed against the Fc portion of immunoglobulin G (IgG) in serum, known as rheumatoid factor (RF). Elevated RF levels are a characteristic serological marker of rheumatoid arthritis (RA), but are not entirely specific. The result is expressed in international units/mL (IU/mL) or units/mL, and a higher titer (concentration) is generally associated with disease severity and the presence of extra-articular manifestations.