Rheumatoid factor

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Rheumatoid factor (RF or RhF) is one of several serological indicators of autoimmunity.[1] It is an antibody against the Fc portion of IgG, which is itself an antibody. RF and IgG join to form immune complexes which contribute to rheumatological diseases.

RF is most commonly measured in patients with suspected rheumatoid arthritis (RA).

RF can be either Type 2 (monoclonal IgM to polyclonal IgG) or 3 (polyclonal IgM to polyclonal IgG) cryoglobulin.

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[edit] Indications

RF is often determined in patients suspected in any form of arthritis. It has relatively little use there, as positive results can be due to other causes, and negative results do not rule out disease. But, in combination with signs and symptoms, it can be diagnostic and prognostic. It is part of the disease criteria of RA.

It is also used in the diagnosis of autoimmune diseases unrelated to arthritis, and sometimes to monitor suspected rejection in certain circumstances of organ transplantation.[1]

[edit] Interpretation

High levels RF (generally above 20 IU/mL, 1:40 or over the 95th percentile there is some variation among labs) are indicative of rheumatoid arthritis (present in 80%) and Sjögren's syndrome[2] (present in almost 100%).[3] The higher the levels of RF the higher the possibility of a more destructive articular disease.

There is a high rate of false positives due to other causes, or when other autoimmune diseases may be present. These include:

[edit] External links

  • MedlinePlus on RF
  • Labtestsonline page on RF
  • Gawlitza G, Wigand R (1976). "[A comparison of two tests for rheumatoid factor: latex test and l-agglutination (author's transl)]". Immun Infekt 4 (1): 23-8. PMID 1254316. 
  • Walid MS, Ajjan M, Patel N: Borreliosis And Human Granulocytic Anaplasmosis Coinfection With Positive Rheumatoid Factor And Monospot Test: Case-Report. The Internet Journal of Infectious Diseases. 2007; Volume 6, Number 1. [1]

[edit] References

  1. ^ a b Rostaing L, Modesto A, Cisterne JM, Izopet J, Oksman F, Duffaut M, Abbal M, Durand D (1998). "Serological markers of autoimmunity in renal transplant patients with chronic hepatitis C". Am J Nephrol. 18 (1): 50-56. PMID 9481439. 
  2. ^ Sjogren's syndrome. Eur J Oral Sci. 2005 Apr;113(2):101-13.
  3. ^ Rheumatoid Factor - Patient UK
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