Rheumatoid Factor

Rheumatoid factors are a heterogeneous group of autoantibodies directed against the antigenic determinants on the Fc-region of IgG molecules. They are important in the diagnosis of rheumatoid arthritis, but can also be found in other inflammatory rheumatic diseases and in various non-rheumatic diseases. They are also found in clinically healthy persons over 60 years of age. Despite these restrictions, the detection of rheumatoid factors is a diagnostic criterion of the American College of Rheumatology for classifying rheumatoid arthritis. The autoantibodies occur in all the immunoglobulin classes, although the usual analytical methods are limited to the detection of rheumatoid factors of the IgM type.

Useful For

In vitro test for the quantitative determination of Rheumatoid Factors (RF-II) in human serum and plasma on Roche/Hitachi cobas c systems. Measurements may be used as an aid in the diagnosis of rheumatoid arthritis.

Method Name

Immunoturbidimetric assay.
Latex-bound heat-inactivated IgG (antigen) reacts with the RF-antibodies in the sample to form antigen/antibody complexes which, following agglutination, are measured turbidimetrically.


Rheumatoid Factor; RF, Rheumatoid Factor - Blood

Specimen Required

Plasma: Li-heparin

Specimen Minimum Volume

0.5 mL of blood

Specimen Stability Information

Stability: 24 hours at 15-25 °C
3 days at 2-8 °C
4 weeks at (-15)-(-25) °C (freeze only once)

Performing Laboratory

As ordered. Turn around time is 8 hours.

Reference Values

< 14 IU/mL