This test is used for the diagnosis of an autoimmune disease termed as rheumatoid arthritis. The test is named after Dr. Erik Waaler (who developed it in 1940) and Dr. H.M. Rose (who modified it in 1948). Rheumatic factor (RF) is found circulating in the blood of RA patients. Rheumatic factor (RF) might be attach to others antibodies because RF is an auto-antibody.
Principle:
It is a slide haem-agglutination method. The Rose-Waaler reagent is a suspension of stabilized sheep red blood cells with rabbit anti-sheep IgG. These cells agglutinate when exposed to rheumatic factor because of a cross-reaction between human and rabbit IgG and as a result agglutination is observed.
Requirements:
- Serum sample
- Rose Waaler reagent
- Positive and negative controls (PC; NC)
- Test card
- Normal saline
- Disposable mixing sticks
- Mechanical rotator (80-100 rpm)
- Test tubes
PROCEDURE:
- Bring the kit reagents and sample to room temperature.
- Place 0.05 ml of the serum into one circle of slide.
- Place similar quantities of positive and negative controls in separate circles.
- Gently mix the antigen vial (to ensure homogeneity) and place one drop to each of the circle.
- Mix the contents of each circle evenly with disposable sticks and spread over the complete area of the circle.
- Place the slide on mechanical rotator (80-100 rpm) for 2 minutes.
- Examine for haem-agglutination macroscopically.
- Compare the results with positive and negative controls.
Results:
Haem-agglutination indicates a positive reaction. If the Rose Waaler test is positive the amount of RF will be equal to 8 IU/ml or above while in case of a negative reaction (no haem-agglutination) less than 8 IU/ml.
Semi Quantitative Test:
If Rose Waaler test is positive, serial dilutions of the serum are tested. The highest dilution of the serum giving positive result will be the titre. Prepare double dilutions of serum as follows:
Quality Control:
Positive and negative controls (animal serum in sodium azide) are included in the kit and must be run parallel to every test performed.
Interpretation of Rose Waaler Test:
- The test is not entirely specific and false positive results are seen commonly (3-5%).
- The test can become positive in following diseases:
- Chronic liver infection
- Leukaemia
- Infectious mononucleosis
- Systemic lupus erythmatosus
- Bacterial endocarditis
- Systemic sclerosis
- Negative results do not rule out the possibility of RA as up to 20% of rheumatoid arthritis patients remain negative for rheumatic factor (seronegative rheumatoid arthritis).
- It is recommended to make the final diagnosis with clinical examination and RF latex agglutination test.
