Rheumatoid Factor

Diagnostic Use

Rheumatoid arthritis (RA) is a chronic inflammatory disease affecting the joints. It is caused when lymphocytes in the synovial membranes produce abnormal IgG antibodies. Rheumatoid factors are autoantibodies of a patients own IgG and IgM that react with the Fc component of the abnormal synovial antigenic IgG to form immune complexes. These immune complexes activate the complement system and other inflammatory systems to cause joint damage.

Rheumatoid factor plays a role in diagnosis of RA and also can serve as a prognostic indicator. High RF concentrations have been associated with a more severe disease course.

Department

Protein Lab

Delphic Registration Code

RHF

Laboratory Handling

Test Adds

Test adds allowable if samples have been stored for 7 days at 2-8 C or frozen at - 20 C for up to 3 months.

Synonyms

RF
RHF

Turnaround Time

5 days

Test Code

6818

Specimen Type

• Serum
• Plasma

Specimen Requirements

Tube/Container Type:

Preferred

• Serum (Red Cap)

Preferred if West Coast

• SST II (Gold Cap)

Acceptable

• SST II (Gold Cap)
• Lithium Heparin - Non-gel (Green Cap)
• Lithium Heparin - Gel (Light Green Cap)
• EDTA (Lavender Cap)

Preferred Sample Volume (ml)

0.5

Minimum Sample Volume (ml)

0.25

No of Samples Required

1

Paediatric Specimen Requirements

Tube/Container Type:

Preferred

• Serum (Red Cap)

Acceptable

• Serum (Red Cap)
• SST II (Gold Cap)
• Lithium Heparin - Non-gel (Green Cap)
• Lithium Heparin - Gel (Light Green Cap)
• EDTA (Lavender Cap)

Preferred Sample Volume (ml)

0.5

Minimum Sample Volume (ml)

0.25

Aliquot Instructions

Sample Type

• Serum
• Plasma

Minimum Volume (ml)

0.25

Transport to Lab

Ambient (8 - 24 degrees Celsius)

Interpretation

High levels of rheumatoid factor are closely associated with autoimmune disease, particularly rheumatoid arthritis. But a number of other diseases and conditions can raise rheumatoid factor levels, including:

Cancer
Chronic infections
Inflammatory lung diseases, such as sarcoidosis
Mixed connective tissue disease
Sjogren’s syndrome
Systemic lupus erythematosus

Some healthy people (particularly older individuals) have positive rheumatoid factor tests, though it’s not clear why. And some people who have rheumatoid arthritis will have low levels of rheumatoid factor in their blood.

Reference Intervals

Reference Interval ≤16 IU/mL

N.B There is no available reference interval for aspirates, as this assay has not been formally validated for this sample type.

Test Method

Nephelometric immunoassay on Siemens BNII nephelometer.

Non-Funded Test Cost

$24.18 (Exclusive of GST)

Billing Code

6818

Measurement uncertainty 10 %

Contact Information

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