Reference Range
Antibodies directed against the Fc fragment of immunoglobulin G (IgG) are called rheumatoid factors (RFs). They are heterogenous and usually composed of immunoglobulin M (IgM). Because of this, most assays detect only IgM. RFs are used as a marker in individuals with suspected rheumatoid arthritis (RA) or other autoimmune conditions.
Normal findings are negative (ie, < 60 U/mL by nephelometric testing). Values may be slightly higher in elderly patients.