Clinical Lab Handbook

Container/Tube: SST

Alternate Container: Light Green (Lithium Heparin), Red Top

Specimen Volume: 5 mL

Collection Instructions: Allow specimen to clot for 30 minutes. Spin specimen in centrifuge.

Centrifuge specimens and remove the serum or plasma from the cellular material within 2 hours of collection.

Two-Point Rate

The VITROS RF Reagent is a dual chambered package containing stable, ready-to-use liquid reagents that are used in a two-step reaction to quantitatively measure rheumatoid factor. In the first step, sample containing rheumatoid factors is diluted with buffer contained in Reagent 1. In the second step, an antigen-antibody reaction occurs between rheumatoid factor from the sample and denatured human IgG adsorbed to latex particles in reagent 2 and agglutination results. The agglutination is detected as an absorbance change at 575 nm with the magnitude of the change being proportional to the quantity of RF in the sample.

Rheumatoid factor (RF) consists of autoantibodies of immunoglobulin isotypes IgM, IgA, IgG, and IgE. 1 The function of RF remains unclear, but it may play a role in the regulation of humoral and cellular immunity and protection against invading microorganisms. Most patients with rheumatoid arthritis and Sjögren’s syndrome have elevated levels of RF. RF may also be elevated in scleroderma, dermatomyositis, Waldenström’s disease, sarcoidosis, and systemic lupus erythematosus. 3 There are also instances of elevated RF without apparent disease or definable clinical disorders.

Limitations: Pathologically high levels of IgG (>2500 mg/dL) may interfere with quantitation of RF.

<12 IU/mL

Monday through Sunday

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