Synonym

• Rheumatoid arthritis factor
• RF

Tubes

• Gel barrier or red top tube
• 5-7 mL of venous blood

Additional information

• Handle sample gently to prevent hemolysis
• Reject lipemic sample

Info

• The Rheumatoid Factor (RF) test detects the presence and levels of RF antibody in the blood
• RF is an anti–gamma-globulin autoantibody usually of IgM class and occasionally of IgG or IgA class. This antibody reacts (binds) to the Fc fragment of IgG to form immune complexes
• Assay techniques used to detect RF include:
• Agglutination of immunoglobulin coated particles (visual assay)
• Latex particle enhanced nephelometry

Clinical

• The clinical utility of the rheumatoid factor (RF) test includes:
• To aid in the diagnosis and evaluation of rheumatoid arthritis (RA)
• To differentiate RA from other forms of arthritis
• For detection of RF in other connective tissue and autoimmune disorders
• Titers can be useful in assessing disease severity and response to therapy
• Initially, patients are screened for the presence of RF. If RF is detected, a titration is performed
• It remains unclear whether RF itself directly causes the destructive changes associated with RA, or is incidental to these changes and could even serve some beneficial purpose
• Absence of RF does not exclude the diagnosis RA as it is a sensitive but nonspecific test
• 5-8% of normal individuals are positive for RF and 15-20% of RA are seronegative for RF
• It is typically for RF to be absent when the first clinical signs and symptoms of RA occur
• Early seroconversion to positive RF is predictive of a greater risk of articular destruction and a sustained disabling course of disease
• RF incidence increases with duration of disease in rheumatoid arthritis
• 3 Months: 33%
• 6 months: 45%
• 1 year: 75%
• 18 months: 90%
• RF is used as a marker for persistence of polyarticular juvenile rheumatoid arthritis into adulthood

Additional information

• Higher values of RF are seen in older individuals (>65 yrs)
• Incidence of RF increases with age
• Conditions not associated with RF include:
• Ankylosing spondylitis
• Chondrocalcinosis
• Enteropathic arthritis
• Gout
• Osteoarthritis
• Psoriatic arthritis
• Suppurative arthritis
• Reiter's syndrome
• Related laboratory tests include:
• Antinuclear antibodies (ANA)
• C-reactive protein
• Cyclic citrullinated peptide antibody (CCP)
• Erythrocyte sedimentation rate (ESR)
• Synovial fluid analysis
• Uric acid

Nl Result

Consult your laboratory for their normal ranges as these may vary somewhat from the ones listed below.

Nephelometry Method

Agglutination Method

High Result

Conditions associated with elevated RA factor include:

• Rheumatoid arthritis (75-90%)
• Collagen-vascular diseases
  • Felty's syndrome
  • Cryoglobulinemia (40-100%)
  • Dermatomyositis (10%)
  • Polyarteritis nodosa
  • Polymyositis (10%)
  • Sarcoidosis
  • Scleroderma (20-30%)
  • Sjögren's syndrome (80-90%)
  • Systemic lupus erythematosus (15-35%)
  • Waldenström macroglobulinemia
• Infectious conditions
  • Bacterial endocarditis (SBE)
  • Influenza
  • Infection following vaccination
  • Kala-azar
  • Leprosy
  • Leishmaniasis
  • Lymphoma
  • Malaria
  • Osteomyelitis
  • Syphilis
  • Tuberculosis
  • Viral infections
    • Adenovirus
    • HIV
    • HCV
    • Mononucleosis
• Hepatic disorders
  • Acute and chronic hepatitis
  • Cirrhosis
  • Primary biliary cirrhosis
• Other conditions
  • Nephrotic syndrome
  • Renal disease
  • Adult Still's disease
  • Diffuse interstitial pulmonary fibrosis
  • Juvenile chronic arthritis
  • Malignancy
  • Myocardial infarction
  • Skin and renal allograft patients
  • Thyroid diseases
• Drugs
  • Methyldopa

Causes of false positive values include:

• Inadequately activated complement
• Individuals who have received multiple vaccinations
• Recent transfusion or multiple transfusions
• Serum with high lipid or cryoglobulin levels

Low Result

• False negative values can occur with high serum IgG levels

References

• Bobbio-pallavicini F et al. High IgA Rheumatoid factor levels are associated with poor clinical response to TNF-{alpha} inhibitors in rheumatoid arthritis. Ann Rheum Dis. 2006 Nov 1; [Epub ahead of print].
• Greiner A et al. Association of anti-cyclic citrullinated peptide antibodies, anti-citrullin antibodies, and IgM and IgA rheumatoid factors with serological parameters of disease activity in rheumatoid arthritis. Ann N Y Acad Sci. 2005;1050:295-303.
• Katwa G et al. False positive elevation of cardiac troponin I in seropositive rheumatoid arthritis. J Rheumatol. 2001;28:2750-1.
• Kobayashi Y et al. [Serum rheumatoid factor and peripheral blood eosinophil counts in patients with bronchial asthma] [Article in Japanese]. Arerugi. 2004;53:1210-5.
• LabTestsOnline®. Rheumatoid Factor. [Homepage on the Internet] ©2001-2006. Last reviewed on September 30, 2006. Last accessed on November 8, 2006. Available at URL: http://www.labtestsonline.org/understanding/analytes/rheumatoid/sample.html
• Spadaro A et al. Interleukin-13 in autoimmune rheumatic diseases: relationship with the autoantibody profile. Clin Exp Rheumatol. 2002;20:213-6.
• UTMB Laboratory Survival Guide®. RHEUMATOID FACTOR, serum. [Homepage on the Internet]© 2006. Last reviewed on February 2006. Last accessed on November 21, 2006. Available at URL: http://www.utmb.edu/lsg/LabSurvivalGuide/chem/RF.html