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rheumatoid factor in serum

Indications: - evaulation of suspected rheumatoid arthritis (RA) Reference interval: - < 40 IU/L - < 14 IU/mL ARUP laboratories [5] Clinical significance: - 70% sensitivity for RA, poor specificity - RF negative RA may later convert to RF positive [3] - RF may be found in synovial fluid & pleural effusions as well as serum - 10% of normal elderly individuals are positive for RF - cyclic citrullinated peptide antibody is a good marker for RA in patients with other disorders also associated with positive RF - elevated rheumatoid factor is associated with an increased risk of developing rheumatoid arthritis [8] Principle: - rheumatoid factor is anti IgG Fc: - immunoglobulin directed against the Fc portion of IgG - RF is often polyreactive with binding to nuclear components as well as IgG - generally RF is of the IgM class, but IgA & IgG RFs have been described. RF Increases: Disorders associated with rheumatoid factor: [2] 1) disorders most likely to have high titers a) rheumatoid arthritis (80%, 50% in elderly) -> often negative in early phases of RA b) Sjogren's syndrome c) mixed cryoglobulinemia d) subacute bacterial endocarditis 2) disorders with low titers a) systemic lupus erythematosus b) scleroderma (systemic sclerosis) c) mixed connective tissue disease d) sarcoidosis e) idiopathic pulmonary fibrosis f) hypergammaglobulinemic purpura g) asbestosis h) malignancies i) infectious mononucleosis j) influenza k) chronic active hepatitis (B & C) l) vaccinations m) tuberculosis n) syphilis o) Brucellosis p) Leprosy q) Salmonellosis r) Malaria s) Kala-azar t) Schistosomiasis u) Filariasis v) Trypanosomiasis w) rubella Methods: 1) agglutination of latex particles coated with IgG 2) nephelometry

Specific

rheumatoid factor IgA in serum rheumatoid factor IgG in serum rheumatoid factor IgM in serum rheumatoid factor in serum qualitative rheumatoid factor in serum quantitative

General

rheumatoid factor (RF) body fluid

References

  1. Clinical Diagnosis & Management by Laboratory Methods, 19th edition, J.B. Henry (ed), W.B. Saunders Co., Philadelphia, PA. 1996, pg 471, 475, 1019
  2. Mayo Internal Medicine Board Review, 1998-99, Prakash UBS (ed) Lippincott-Raven, Philadelphia, 1998, pg 826
  3. Medical Knowledge Self Assessment Program (MKSAP) 11, 17. American College of Physicians, Philadelphia 1998, 2015
  4. Panel of 4 tests Laboratory Test Directory ARUP: 50119
  5. Rheumatoid Factor Laboratory Test Directory ARUP: 50465
  6. Mini Panel of 2 tests: Rheumatoid Factor . Cyclic Citrullinated Peptide Ab, IgG Laboratory Test Directory ARUP: 2003277
  7. Mini Panel of 2 tests: Rheumatoid Factor . Cyclic Citrullinated Peptide Ab, IgG Laboratory Test Directory ARUP: 2003278
  8. Nielsen SF et al. Elevated rheumatoid factor and long term risk of rheumatoid arthritis: A prospective cohort study. BMJ 2012 Sep 6; 345:e5244 PMID: 22956589 - Simard JF and Holmqvist M. Rheumatoid factor positivity in the general population. BMJ 2012 Sep 6; 345:e5841 PMID: 22956591