SERION RF Absorbent 

Rheumatoid factors are autoantibodies mainly of the IgM class that can be detected in serum samples of approximately 5 % of healthy individuals. Those IgM rheumatoid factors bind preferably to IgG immune complexes. Therefore, false positive results may appear in pathogen-specific IgM detection. In samples with high concentrations of pathogen-specific IgG antibodies, weak binding pathogen-specific IgM antibodies may be displaced by stronger binding IgG antibodies. In those cases, IgM detection can show false negative results. Therefore, it is necessary to pretreat serum samples with rheumatoid factor-absorbent prior to pathogen-specific IgM detection. Up to 15 mg/ml IgG antibodies and thereby also the attached rheumatoid factors can be precipitated from undiluted serum.

RF absorption is performed by incubation of the patient sample in RF-dilution buffer for 15 minutes at room temperature or overnight at 4 °C. The test procedure is described in a separate instruction manual.