A B C D E F G H I J K L M N O P Q R S T U V W X Y Z # |
Rheumatoid Factor (IgA, IgG, IgM)
Test Code19705
CPT Codes
83520 (x3)
Includes
Rheumatoid Factor (IgA)
Rheumatoid Factor (IgG)
Rheumatoid Factor (IgM)
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
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®)
Methodology
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