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Microbiology Presentations

Rheumatoid Factor (RA Factor) and Its Diagnostic Importance

  • October 13, 2013
  • 2 min read
Rheumatoid Factor (RA Factor) and Its Diagnostic Importance

A presentaion on rheumatoid factor and its significance in diagnosis of rheumatoid arthritis by students of Kist Medical College


  • To define Rheumatoid Factor .
  • To explain briefly its significance in the diagnosis of rheumatoid arthritis.

Rheumatoid factor

  • Rheumatoid factor (RF) is an autoantibody that is directed against organism’s own tissues, most relevant in rheumatoid arthritis.
  • An antibody against the Fc portion of IgG, which is itself an antibody. RF and IgG join to form immune complexes which contribute to the disease process.

Diagnosis of RA

  • Diagnosis is based on clinical test, signs and symptoms and imaging technique.
  • The test for RF may be ordered when a person has signs of RA.
  • Symptoms : pain, warmth, swelling, and morning stiffness in the joints, nodules under the skin
  • X-rays of swollen joint capsules
  • An RF test may be repeated when the first test is negative and symptoms persist.

Significant associations

  • Rheumatoid disease including Rheumatoid Arthritis .
  • Higher the level of RF, the worse the joint destruction and greater the chance of systemic involvement.


  • Rheumatoid arthritis (60-70%)
  • Sjögrens syndrome (≤100 %)
  • Felty’s syndrome (≤100 %)
  • Systemic sclerosis (30%)
  • Infective endocarditis (≤ 50%)
  • Systemic lupus erythematous (≤ 40%)
  • Infectious mononucleosis
  • Hepatitis
  • TB
  • Cancer

RF Test

  • RF is commonly used as a blood test for the diagnosis of rheumatoid arthritis.
  • A negative RF is seronegative , in about 15% of patients.
  • During the first year of RA, RF is more likely to be negative but some individuals convert to seropositive later.


  • High levels of rheumatoid factor
  • Generally above 20 IU/mL
  • Upto dilution level 1:40 (of rheumatoid factor)
  • In 80% cases

Other Serological Tests

  • New test for the presence of anti-citrullinated protein antibodies (ACPAs).
  • ANA (antinuclear antibody)
  • CRP (C-reactive protein)
  • ESR (erythrocyte sedimentation rate)
  • CBC (Complete Blood Count)


  • Rheumatoid factor (RF) an antibody ( IgM )
  • It is used for the diagnosis of Rheumatoid arthritis
  • But it is not the confirmational test because it is observed in other related and unrelated diseases

Prepared by:
Samjhana Sharma (73)
Sashi Kumar Yadav (74)
Sat Prasad Nepal (75)
Sharmila Phellu (76)
Shraddha Shrestha (77)
Shuvechha Pandey (78)
Srijana Shakya (79)
Sulabh Shrestha (80)
Surakshya Rayamajhi (81)
Surendra Pariyar (82)
Sushil Dulal (83)
Sushmita Bajagain (84)
Tulsi Ram Shrestha (85)
Uday Chandra Prakash (86)

First Published in 2010, Republished 2013

About Author

Sulabh Shrestha

Intern doctor and Medical Blogger Sulabh Shrestha


  • Dear all, a nice crisp summary on RF.. Juz note the use of term “rheumatoid factor” which is very correct and the use of term RA factor is wrong..there is nothing like rheumatoid arthritis factor! Second, it may be negative in 15-25% ie patient still has RA despite RF negativity. Also it is positive in around 10-15% of those without arthritis. In case of confusion send ACPA to confirm which has 95% sensitivity.
    Also, majority of RF are IgM Ab but some can be IgA and IgG too (which are not detected routinely).

    Dr Binit Vaidya, MD FACR

  • gud one!!!

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