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Rheumatoid Factor Test – The Complete Understanding Guide

In Rheumatoid Factor Test, we measure the amount of rheumatoid factor in our blood. Our immune system is responsible to produce rheumatoid factors which are known as the protein that can affect the healthy tissue of our body.

If the level of rheumatoid factor found high, it results in autoimmune diseases, such as rheumatoid arthritis and Sjogren’s syndrome. But rheumatoid factor may be found in normal people and sometimes. Rheumatoid arthritis is a chronic systemic disease. It often has swelling and pain problems in the joints and is caused by inflammatory and degenerative processes involving the cartilage, synovial membrane or muscle tissue.

The disease is widespread in the United States and worldwide and occurs in all age groups. Usually, it starts in young adults in their thirties and forties. Although no specific treatment has yet been found, early therapy is very important to prevent or reduce irreversible damage to the joints. For this reason, early diagnosis is of great importance.

A feature of rheumatoid arthritis is the presence of the hood and inside the synovial fluid of a reactive group of proteins called the rheumatoid factor. This Macroglobulin has a molecular weight of 1 million.

According to many Investigator, rheumatoid factors are antibodies which directed against “manipulated” human gamma globulins. Rheumatoid factors found 70-100% of cases of definitive rheumatism on a trial basis of the process used to detect them.

Due to this widespread occurrence of RF, It’s performance is a useful laboratory criterion for the diagnosis of suspected arthritis. By comparison, the occurrence of RF in arthritis or Rheumatic fever is less than 2 and 3% respectively.

It should be noted that the occurrence of RF has been reported in a variety of non-infectious diseases such as pulmonary tuberculosis, bacterial endocarditis and syphilis as well other.

A significant incidence of RF has also been observed in the elderly. Since the discovery of RF, many technologies have evolved to Identifying and quantifying these factors. Most commonly used techniques Agglutination processes employing polystyrene particles are with a layer of absorbed human gamma globulin.

RF present in a test serum reacts with the coating material causing visible agglutination of the inert latex particles. It is the reaction which is based on CENOGENICS ‘ RFTEST. CENOGENICS’RFTEST set to detect rapid rheumatism factor and one of the criteria for diagnosis, accurately identifies the presence of RF of rheumatism.

In the presence of rheumatoid factor positive antiserum, CENOGENICS ‘ Latex – globulin RF reagent can be used to demonstrate both agglutinations Qualitatively and quantitatively.

Rheumatoid Factor Test - The Complete Understanding Guide

Arthritis factor testing is one of a group of blood tests that are mainly used to help in the diagnosis of rheumatoid arthritis. These other tests may include:

  • Anti-nuclear antibody (ANA)
  •  Anti-cyclic citrullinated peptide (anti-CCP) antibody
  •  C-reactive protein (CRP)
  • Erythrocyte sedimentation rate (ESR)

The amount of rheumatoid factor in your blood can also help your doctor choose the treatment approach that will work best for your condition.

Principle of Rheumatoid Factor Test

The principle of the test is the rheumatoid factor (RF), an immunological reaction between a macromolecular molecule globulin found in serum and corresponding lgG coated on finely dispersed polystyrene latex particles.

Reagents Used in Rheumatoid Factor Test

  • RF latex direct reagent: In this Reagent, the polystyrene latex particles which coated with serum human lgG and suspended in a glycine buffer is present.
  • Positive control serum: In this reagent, a stabilized human serum containing rheumatoid factors reactive with the latex reagent.
  • Negative control serum: In this reagent, a stabilized human serum nonreactive with the latex reagent.

Note: All reagents are preserved with the help of sodium azide (1mg/ml).

Material Required in Rheumatoid Factor Test

  • RF Latex Direct Reagent
  • Positive Control Serum
  • Negative Control Serum
  • 6- Well Test Slide
  • Disposable Pipettes
  • Product Instructions
  • Test Tubes (for quantitative method)
  • Serological Pipettes
  • Laboratory Timer
  • Laboratory Rotator (optional)
  • Isotonic Saline (0.85%’sodium chloride, for quantitative method)

Precautions while Performing RA Factor Test

  • For in-vitro diagnostic use.
  • Do not use beyond the expiration date.
  • Handle all samples of human origin such as the capsule of infection disease.
  • Reagents in this kit contain sodium azide. Sodium azide can react with lead and copper pipelines to form highly explosive metal oxides. Upon disposal, flush with a large amount of water to prevent the formation of oxide.
  • Sensitivity – 8 lU/ml with a tolerance of 6-16 lU/ml calibrated against the WHO international RA standard.
  • Storage Conditions – Store at 2- 8degree celsius.
  • Stability– The expiration date is specified on the label. Biological indication of product volatility is evidence of improper reaction of latex reagent with corresponding positive and negative controls.
  • Reagent Preparation – Reagents are ready to use, no reagent preparation is required.
  • Specimens – This test should be performed on fresh serum. The samples may be stored refrigerated (2″ – 8″C) for a maximum of 7 day

Also Read: Complement Fixation Test – Principle, Components, Procedure, Advantages, Disadvantages

Procedure for Qualitative Method of RA Factor Test

  1. Allow all the reagents and samples to room temperature.
  2. Shake the latex reagent gently, take out the contents of the dropper and refill.
  3. Distribute on the drop (50 UD of patient samples in a circle on the test slide). Use a new pipette for each sample.
  4. Using the dropper provided, place a drop of latex reagent next to each sample on the test slide.
  5. Combine each sample and latex with a disposable Stirrer and spread over the entire surface of each circle.
  6. Rotate the slide for 2 minutes.
  7. Check under the presence of a bright light source for the presence of agglutination.

Results of Qualitative Method of RA Factor Test

Positive Results: Agglutination (clumping of the latex particles) indicates a positive result. A weakly reactive serum produces a very fine granulation or partial clumping.

The Results of a positive rheumatic factor test indicated that a high level of a rheumatoid factor was detected in your blood. A high level of rheumatoid factor in your blood is closely associated with autoimmune disease, especially rheumatoid arthritis.

But rheumatoid factors can increase levels in many other diseases and conditions, including:

  • Cancer
  • Chronic infection
  • Inflammatory lung diseases, such as sarcoidosis
  • Mixed connective tissue disease
  • Sjogren’s syndrome
  • Systemic lupus erythematosus

Some healthy people – especially older individuals – have positive rheumatic factor tests, although it is unclear why. And some people who have rheumatoid arthritis will have low levels of rheumatoid factor in their blood.

Negative Results: The absence of agglutination indicates a negative result.

Quality Control

  • Positive control and negative control should be tested with each series of test sera. The controls supplied by CENOGENICS are to be used exactly as outlined in steps 1 thru 4 above without further dilution.
  • A positive control will produce agglutinated flocs. A negative control will produce no agglutination. It should be used as a basis for comparison. The relative degree of smoothness of the reagent itself should be considered and incorporated in reading the results.
    If the indicated results, using the positive and negative controls are not obtained, the RF Latex Kit should not be used.

Procedure for Semi-Quantitative Method of RA Factor Test

  • Using isotonic saline (0.85% sodium chloride), prepare a serial dilution of the serum starting at 1:2 to l:64.
  • The test of each dilution performs described as in the Qualitative Procedure.


The titre is reported as the reciprocal of the highest dilution which gives a visible agglutination.

Limitation for this Procedure

The detection limit for RF latex direct test of CENOGENICS is 8 lU/ml. In a comparison study between CENOGENICS’s RF latex direct test and a commercially available product, the agreement was 98.8%.

Expected Values and Performance Characteristics

The clinical significance of RF fixation lies in the differentiation between rheumatism in which serum has been demonstrated in approximately 80% of cases of rheumatoid factor examined and rheumatic fever in which rheumatic factor is almost always absent. RF is more often inactive proc € ss Have longer duration than diseases that are less active or still in infancy.

It is sometimes found in the serum of patients with a variety of chronic inflammatory diseases such as polyarthritis nodosa, systemic lupus erythematosus, and tuberculosis, leprosy, syphilis, and bacterial endocarditis. Serra tested with these related diseases showed positive reactions in about 6% of Test cases.

Approximately 3.5% of known rheumatic patients do not respond to screening tests, on the other hand, 2% of sera from apparently healthy individuals responded to RF.

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