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Immunology Laboratory

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Rheumatoid factor

Also known as: RhF

Rheumatoid factor (usually IgM) is present in approximately 70% of patients with RA and correlates with more severe disease. The presence of RF is not essential for the diagnosis of RA. RF also occurs in other autoimmune diseases (SLE, scleroderma, Sjogren's), and chronic bacterial infection. Rheumatoid factors are present in low titre in 5% of the normal population.

Specimen requirements

Serum 1ml


Price on application

Laboratory turnaround time

3 days

Laboratory method


Reference range/units

<30 IU/mL = negative

30-50 IU/mL = weak positive

>50 IU/mL = positive

Associated tests

Not applicable

Sample stability

2 weeks at 2-8ÂșC

Shipping and storage

UK and Ireland

Ambient temperature and first class post. Hays DX users please enquire via email below.


Ambient temperature if courier will deliver within 72 hours otherwise consider refrigerated transport. Freezing is not a requirement.

Ensure delivery Monday to Friday 09:00 - 17:30.

Further information and contact details

For further information, email

Last reviewed:09 October 2023