Rheumatoid Factor

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.
Reference range: 

Normal limit < 20 iu/mL

Sample type and Volume required: 
Clotted (Gold top vacutainer)
Turnaround time: 
2 working days
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.

Storage and transport: 
Samples may be stored at 4°C prior to analysis
Time limit for extra tests: 
10 days
Diagnostic Immunology and Allergy Department at King's College Hospital
General Enquiry : 020 3299 8752 / 020 3299 1171
King's College Hospital
Bessemer Wing - 1st Floor
Denmark Hill
London SE5 9RS
For clinical advice or interpretation of results, please contact the laboratory in the first instance.

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Last updated: 07/08/2015