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Test Code RHUT Rheumatoid Factor, Serum

Reporting Name

Rheumatoid Factor, S

Useful For

Diagnosis and prognosis of rheumatoid arthritis

Performing Laboratory

Mayo Medical Laboratories in Rochester

Specimen Type


Specimen Required


Preferred: Serum gel

Acceptable: Red top

Specimen Volume: 1 mL

Specimen Minimum Volume

0.5 mL

Specimen Stability Information

Specimen Type Temperature Time
Serum Refrigerated (preferred) 14 days
  Ambient  14 days
  Frozen  14 days

Reference Values

<15 IU/mL

Day(s) and Time(s) Performed

Monday through Friday; Once a day

Test Classification

This test has been cleared or approved by the U.S. Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
RHUT Rheumatoid Factor, S 11572-5


Result ID Test Result Name Result LOINC Value
RHUT Rheumatoid Factor, S 11572-5

Clinical Information

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.


A variety of tests for the determination of RF have been described including agglutination of sheep erythrocytes that have been sensitized with rabbit IgG; and agglutination of polystyrene latex particles that have been coated with human IgG; as well as radioimmunoassay and enzyme immunoassays.


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.


Positive results are consistent with rheumatoid arthritis.

Clinical Reference

1. Winchester RJ: Characterization of IgG complexes in patients with rheumatoid arthritis. Acad Sci 1975;256:73-81

2. Roberts-Thomson PJ, McEvoy R, Langhans T, Bradley J: Routine quantification of rheumatoid factor by rate nephelometry. Ann Rheum Dis 1985;44:379-383

Analytic Time

2 days

Reject Due To


Mild OK; Gross OK


Mild OK; Gross reject


Mild OK; Gross OK



Method Name