Test Overview
Test Methodology


Test Usage

To determine the presence of 19S gamma globulins directed against IgG Immunoglobulins, to support the diagnosis of rheumatoid arthritis, to evaluate ankylosing spondylitis and sacroilitis. Strong positivity with low ANA usually means rheumatoid arthritis.

Reference Range *

< 12 IU/mL

* Reference ranges may change over time. Please refer to the original patient report when evaluating results.

Test Limitations

A very low value may exist in a variety of other diseases. Weak RF, high ANA and anti-n-DNA, and low complement levels may indicate SLE. Weak RF and low ANA may indicate cryoglobulinemia, vasculitis, or both. RF is not specific for a diagnosis of rheumatoid arthritis. There are numerous cases of sero-negative rheumatoid arthritis. Patients with collagen diseases other than RA may have RF.

Test Details
Days Set Up
Monday - Friday
Analytic Time

8 hours

Soft Order Code
MiChart Code
Rheumatoid Factor
  • RA
  • RF
  • RF Test
  • Rheumatoid Arthritis
  • Rheumatoid Factor
  • SCAT Replacement Assay
  • Sheep Cell Agglutination Titer Replacement Assay
Chemical Pathology
Specimen Requirements
Collection Instructions

Collect blood in SST tube. Centrifuge, aliquot serum into a plastic vial and refrigerate. Fluids are not acceptable.

Normal Volume
0.5 mL serum
Minimum Volume
0.3 mL serum
Rejection Criteria
Fluids are not acceptable.
Additional Information

False negatives or weak reactions may be attributed to early or chronic stages of the disease or to therapy. False positives may occur in pulmonary TB, SLE, aging, syphilis, cirrhosis, infectious hepatitis, viral infections, mixed cryoglobulinemia, and myeloproliferative disorders. RF is reported in 70-80% of clinically diagnosed RA cases. Some rheumatoid factors react as cryoglobulins and may be a clue to the presence of cryoglobulinemia. These are anti-IgG antibodies complexed with IgG that form precipitates at low temperatures.

CPT Code
Fee Code