Rheumatoid factor (RF) is an autoantibody with specificity for the Fc region of IgG. The RF tested for in the laboratory is IgM anti-IgG Fc. IgA and IgG rheumatoid factor have been described. IgM RF is included ACR/EULAR 2010 Rheumatoid Arthritis Classification Criteria but is not diagnostic of RA as it is present in other autoimmune disorders, chronic infection and up to 10% of apparently normal adults.
Related condition
Rheumatoid arthritis
Reference range
Normal limit < 20 iu/mL
Units
IU/ml
Testing site
Synnovis : Reference Services : Blackfriars Hub
Laboratory
Diagnostic Immunology
Sample type and volume required
Clotted (Gold top vacutainer)
Special sample instructions
All tests are compromised by prolonged transit times. For this reason, date of bleed and date of postage must be provided with each request.
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