II. Mechanism

  1. Polyclonal B Cell activation synthesizes RF autoantibody
  2. RF IgM (rarely IgG) Antibody
    1. Binds IgG constant region (crystallizable fragment)
  3. Serum Detection
    1. Latex fixation
      1. Agglutination of latex particles
      2. Latex coated with human IgG
    2. Sheep Cell Agglutination Assay indications
      1. Negative latex fixation despite high suspicion

III. Causes: Negative

  1. Normal
  2. Conditions in which Rheumatoid Factor is expected to be negative
    1. Osteoarthritis
    2. Ankylosing Spondylitis
    3. Gout
    4. Chondrocalcinosis
    5. Suppurative Arthritis
    6. Psoriatic Arthritis
    7. Enteropathic Arthritis
    8. Reiter's Syndrome

IV. Causes: Positive

  1. Rheumatoid Factor present in normal persons
    1. Very Low titers (<1:80) present in many patients
    2. Normally present in 1-5% of general population
    3. Incidence of RF increases with age
    4. Incidence of RF increases in age over 65 years: 10%
  2. Rheumatoid Arthritis (33-90%)
    1. RF Titer alone does not diagnose Rheumatoid Arthritis
      1. Test Sensitivity: 69%
      2. Test Specificity: 85%
      3. Positive Likelihood Ratio (LR+): 4.86
      4. Negative Likelihood Ratio (LR-): 0.38
    2. Prognosis worse with high titer at onset
      1. Higher titers are associated with erosive Arthritis, extraarticular involvement
    3. RF Incidence increases with duration of disease
      1. Three months: 33%
      2. Six months: 45%
      3. One year: 75%
      4. Eighteen months: 90%
      5. Up to 20% of RA patients remain seronegative
  3. Other Autoimmune Disease
    1. Sjogren's Syndrome (75 to 95%)
    2. Systemic Lupus Erythematosus (15 to 35%)
    3. Scleroderma (20 to 30%)
    4. Polymyositis or Dermatomyositis (10%)
    5. Cryoglobulinemia (40 to 100%)
    6. Mixed Connective Tissue Disease (50 to 60%)
  4. Infections
    1. Bacterial Endocarditis
    2. Osteomyelitis
    3. Tuberculosis
    4. Syphilis
    5. Hepatitis (Acute and Chronic)
    6. Mononucleosis
    7. Parasitic Infection
    8. Viral Infection (esp. Mumps, Rubella, Influenza)
  5. Lung Disease
    1. Asbestosis
    2. Diffuse interstitial pulmonary fibrosis
    3. Sarcoidosis
    4. Silicosis
  6. Gastrointestinal Conditions
    1. Hepatic Cirrhosis
    2. Primary biliary Cirrhosis
  7. Cancer
    1. Leukemia
    2. Colon Cancer

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Definition (NCI) Antibodies in the serum of individuals with rheumatoid arthritis that react with antigenic determinants or immunoglobulins that enhance agglutination of suspended particles coated with pooled human gamma -globulin. Rheumatoid factors also occur in other autoimmune and certain infectious diseases.
Definition (CSP) antibodies directed against antigenic determinants in the Fc region of IgG, frequently found in the serum of patients with rheumatoid arthritis and other connective tissue diseases.
Definition (MSH) Antibodies found in adult RHEUMATOID ARTHRITIS patients that are directed against GAMMA-CHAIN IMMUNOGLOBULINS.
Concepts Amino Acid, Peptide, or Protein (T116) , Immunologic Factor (T129)
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SnomedCT 143242007, 165838007, 77089006
LNC LP16738-4, MTHU001879
English Factor, Rheumatoid, Rheumatoid Factor, Rheumatoid Factor [Chemical/Ingredient], rheumatoid factor, rheumatoid factors, RF, Factor - rheumatoid, Rheumatoid factor, RF - Rheumatoid factor, RhF - Rheumatoid factor, Rheumatoid factor (substance)
Swedish Reumatoid faktor
Czech revmatoidní faktor
Finnish Reumatekijä
Polish Czynnik reumatoidalny
Portuguese Fator Reumatoide
Spanish factor reumatoide (sustancia), factor reumatoide, Factor Reumatoide
French Facteur rhumatoïde
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Ontology: Rheumatoid Factor Measurement (C0201660)

Definition (NCI) The determination of the amount of rheumatoid factor antibody present in a sample.
Definition (NCI_CDISC) A measurement of the rheumatoid factor antibody in a biological specimen.
Concepts Laboratory Procedure (T059)
SnomedCT 165847004, 143249003, 54921001
CPT 86431, 1011965
English Rheumatoid factor, Factor rheumatoid, Rheumatoid Factor Measurement, factor rheumatoid test, rheumatoid factor, Test;rheumatoid factor, test rheumatoid factor, factor rheumatoid testing, Rheumatoid factor level, Rheumatoid factor titer, Rheumatoid factor NOS (procedure), Rheumatoid factor NOS, Rheumatoid Factor, RF, Rheumatoid Factor Test, Rheumatoid factor measurement (procedure), Rheumatoid factor measurement, Rheumatoid factor measurement, NOS, rheumatoid factor test
Italian Fattore reumatoide
Dutch factor reuma, reumatoïdfactor
Japanese リウマチ因子, リウマトイド因子, リウマチインシ, リウマトイドインシ
Czech Revmatoidní faktor, Faktor revmatoidní
Hungarian Rheumatiod faktor, Rheumatoid faktor
Spanish determinación de factor reumatoideo, SAI, Rheumatoid factor NOS, determinación de factor reumatoideo, SAI (procedimiento), medición de factor reumatoideo (procedimiento), medición de factor reumatoideo, Factor reumatoide
Portuguese Factor reumatóide
French Facteur rhumatoïde
German Rheumafaktor