Rheumatoid Factor (IgA, IgG, IgM) [19705]

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Test Code

Alias/See Also

CPT Codes
83520 (x3)

Rheumatoid Factor (IgA)
Rheumatoid Factor (IgG)
Rheumatoid Factor (IgM)

Preferred Specimen
1.8 mL serum collected in a red-top tube (no gel)

Patient Preparation
Overnight fasting is preferred

Minimum Volume
0.9 mL

Transport Container
Plastic screw-cap vial

Transport Temperature
Refrigerated (cold packs)

Specimen Stability
Room temperature: 48 hours
Refrigerated: 8 days
Frozen: 28 days

Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Gross hemolysis • Grossly lipemic • Grossly icteric • Heat treated samples • Serum separator tube (SST®)

Immunoassay (IA)

Setup Schedule
Set up: Tues, Sat; Report available: 1-4 days

Reference Range
Rhematoid Factor (IgA)
≤6 Negative
>6 Positive
Rhematoid Factor (IgG)
≤6 Negative
>6 Positive
Rhematoid Factor (IgM)
≤6 Negative
>6 Positive

Clinical Significance
The concentration of RF tends to be highest when the disease peaks and tends to decrease during prolonged remission. RF IgM is found in 1 to 4% of the general population. RF is present in 75% of adult RA patients with the highest incidence of RF occurring in persons over 65 years of age. Increased RF levels may also accompany a variety of acute immune responses, particularly viral infections and a number of liver diseases (infectious mononucleosis, tuberculosis, leprosy, various parasitic diseases, liver disease, sarcoidosis, and systemic lupus erythematosus).

In addition to RF IgM, raised levels of RF IgA and IgG have been reported in patients with RA. Studies from as early as 1984 suggest that the detection of RF IgA in early disease indicates poor prognosis and justifies a more aggressive course of treatment. Recently, it has become apparent that the specificity and predictive value of the RF test is substantially increased by the detection of all three RF isotypes.

Performing Laboratory
Quest Diagnostics Nichols Institute
14225 Newbrook Drive
Chantilly, VA 20153

Last Updated: December 6, 2021

The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.