1. Test for Rheumatoid Factors
Lesson 4-3
Test for Rheumatoid Factors

2. Rheumatoid Arthritis (RA)
Autoimmune disease
Joint inflammation, pain, and deformity
Distinguish from other types of arthritis

3. Rheumatoid Arthritis (RA)
Rheumatoid factors (RF)
IgM directed against IgG
Detect using rapid tests
75% to 85% of RA patients have
elevated serum RF
RF present in other conditions

4. Principle of RF Slide Test
Latex agglutination
Reagent is IgG-coated latex particles
Combine patient serum with latex reagent
Observe for agglutination
RF (IgM) will cause agglutination

5. Principle of RF Slide Test

6. Qualitative Test for RF
Safety precautions
Quality assessment
Specimen
Serum from venipuncture
Dilute serum 1:20
Procedure
Diluted serum + latex reagent

7. Interpreting Results of RF Test
Agglutination is positive (+) result
Perform semi-quantitative test if 1:20 dilution is positive

8. Significance of Results
Only serum positive at ≥1:20 is considered positive for RF
Conditions other than RA can cause positive results
15% to 25% of RA patients can be negative for RF

9. Semi-Quantitative Test for RF
Serial dilutions of patient serum
Test each dilution with latex reagent
Report RF titer
Identify highest dilution with positive reaction
Titer is reciprocal of dilution

10. Significance of Positive RF Test
RF test not specific for RA
Only 75% to 85% positive in RA patients
Negative test does not rule out RA
Other conditions can have ↑ RF
Test can be used to follow disease
course
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