Rheumatoid factor is an antibody that is associated with rheumatoid arthritis. A test called the rapid latex agglutination test can detect rheumatoid factor in a patient's serum. This test works by mixing the patient's serum with latex particles coated with human IgG - if rheumatoid factors are present, the latex particles will agglutinate or clump together visibly. Controls and following the correct procedure are important to ensure accurate results. While rheumatoid factor can indicate rheumatoid arthritis, some patients may not have it present and it may be detected in other diseases as well.

1. Rheumatoid Factor

2. Introduction
• Rheumatoid factors are antibodies with specificity
for antigen determinants on the Fc fragment of
human or certain animal IgG.
• They’re associated with IgG, IgM & IgA. IgG & IgM
rheumatoid factors are the most common.
• During some disease of a joint, rheumatoid
arthritis, an IgG antibody is produced following to
its production the antibody become altered for
unknown reason, against this altered antibody a
second antibody (anti antibody) is produced which
is known as antigammaglobulin antibody.

3. Test for Rheumatoid arthritis
• Rapid latex agglutination
• Principle: The test is based on the reaction
between patient antibodies in the serum,
known as the rheumatoid factor; and an
antigen derived from gamma globulin. If
rheumatoid factors are present in the serum,
macroscopic agglutination will be visible when
the latex reagent is mixed with the serum.
• Specimen: Serum

4. Reagents & materials required
• Latex reagent
• Glycine saline buffer
• Capillary pipette
• Applicator stick
• Glass slide
Additional required equipment
• Timer
• Test tubes
• Serologic pipette
• Positive control
• Negative control

6. PROCEDURE
• A. FOR QUALITATIVE TEST

8. PROCEDURE

9. Reporting results
• Positive reaction: agglutination of the latex
suspension indicates the presence of
rheumatoid factor in the specimen. Negative
reaction: absence of visible agglutination.

10. STORAGE AND STABILITY

11. QUALITY CONTROL
• RF Positive and Negative Control should be
included in each test batch.
• Acceptable performance is indicated when a
uniform milky suspension with no
agglutination is observed with the RF Negative
Control and agglutination with large
aggregates is observed with the RF Positive
Control.

12. LIMITATIONS
• Reaction time is critical. If reaction time
exceeds 2 minutes, drying of the reaction
mixture may cause false positive result.
• Increased levels of RF may be found in some
diseases other than rheumatoid arthritis such
as infectious mononucleosis.
• Certain patients with rheumatoid arthritis will
not have the RF present in their serum.