Yale New Haven Hospital

Department of Laboratory Medicine
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Rheumatoid factor

Lab Section: 



Lab Location: 

Main Lab

Test ID: 








2 days

Specimen Requirements: 

Collection: 5.0 mL Blood in a Gold Top Tube.
Pediatric volume: 0.5 mL.
Unacceptable conditions: Grossly hemolyzed specimens.
Stability: After separation from cells: Ambient: 48 hours; Refrigerated: 7 days; Frozen: 3 months



Clinical Indications: Rheumatoid factors (RF) are antibodies that are directed against the Fc fragment of IgG altered in its tertiary structure. Although the IgM class is the most common RF, IgG and IgA RFs have been reported. Over 75% of patients with rheumatoid arthritis (RA) have an IgM antibody to IgG immunoglobulin. This autoantibody (RF) is diagnostically useful although it may not be etiologically related to RA. The titer of RF correlates poorly with disease activity, but those patients with high titers tend to have more severe disease and thus a poorer prognosis than do sero-negative patients. Tests are usually positive for patients with nodules or clinical evidence of vasculitis.

Reference Interval: 

<15.9 IU/mL >

<15.9 IU/mL

CPT Code(s): 


Last Changed: 

7/2/2018 3:48 PM

Last Reviewed: 

8/24/2017 12:31:10 PM