Principle

Rheumatoid factor latex test kit consists of polystyrene latex particle coated with specially modified preparation of human gammaglobulin (IgG) in order to avoid non specific agglutination.

The suspension of coated latex particles agglutinate visible when mixed with serum containing rheumatoid factor. The sensitivity of reagent has been adjusted to detect=10IU/ml of RF calibrated against an international standard.

Specimen: Use fresh serum specimen

Requirements

1. Latex reagent
2. Positive control
3. Negative control
4. Glass slide
5. Disposable applicator stick
6. Disposable plastic dropper
7. Rubber teats

Procedure

A. Qualitative method:

1. Bring all reagent as well as the samples at room temperature (+15°C to +30°C).
2. Using the disposable plastic dropper, place one drop of test serum within the circled area marked      TEST on the special slide provided in the kit.
3. Shake the vial gently and add one drop of latex gammaglobulin reagent (using the dropper provided in vial      Cap =40μl) to the above drop and mix well with a disposable applicator stick.
4. Rock the slide gently to and for 2 minutes&examine for agglutination.
5. Do not examine beyond 2 minutes.

Result

Result should be read within 2 minutes.

Clearly visible agglutination indicates a positive granularity of doubtful clumping should be ignored

B. Semi Quantitative method

 To determine the titer (i.e. the highest dilution showing visible agglutination prepare serial doubling       test serum using normal saline, from 1:2 doubling up to 1:128 or as needed.

1. Place one drop of each dilution of serum within the respective marked area of special slide in the kit.
2. Add one drop of thoroughly mixed latex gammaglobulin reagent and mix well with disposable applicator           stick. Use separate stick for each serum dilution.
3. Gently rock the slide to and fro and observe agglutination for no longer than 2 minutes. 

Absent in cases of  rheumatic fever. The latex agglutination test does not provide the final diagnosis of n      rheumatoid arthritis. And therefore, it should be used only in conjunction with proper clinical evaluation.

Observation

A. Qualitative test

Result

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B. Semi-quantitative test:

Result

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Conclusion

Clinical significance: Because of the delayed appearance of the rheumatoid factor (RF), it is more frequently present in chronic active phases of the disease than in the early or in the sub-clinical chronic phases of rheumatoid arthritis.

Rf is also found in many cases of autoimmune diseases like systematic Lupus erythematosus (SLE), scleroderma and Sjogren’s syndrome, weekly positive latex Agglutination test for rheumatoid factor has occasionally been observed in some sera of patients with Hepatitis, Sarcoidosis, Cirrhosis of liver, Syphilis, Hypergammaglobulinemia, acute bacterial and viral infection. 

Reference

KIT USED-ARKRAY HEALTHCARE PVT.LTD

                    RHEUMATOID ARTHRITIS (RF) LATEX TEST.