rheumatoid factor

noun

: an autoantibody of high molecular weight that reacts against IgG immunoglobulins and is often present in rheumatoid arthritis

Examples of rheumatoid factor in a Sentence

Recent Examples on the Web
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These include tests that look for rheumatoid factor, anti-CCP antibodies, and the HLA-B27 gene.5 Imaging: Your healthcare provider may want an X-ray, magnetic resonance imaging (MRI) scan, or ultrasound of your affected joints. Mark Gurarie, Health, 27 June 2025 It is classified into two subtypes: rheumatoid factor positive (RF) and rheumatoid factor negative.3 RF is an antibody that contributes to long-term inflammation. Lana Barhum, Verywell Health, 26 Sep. 2024 One of these blood tests measures the amount of rheumatoid factor (RF), a protein produced by your immune system that can attack healthy tissue, in your body. Women's Health, 4 Apr. 2023 Nearly everyone who is evaluated for psoriatic arthritis will have their blood tested for rheumatoid factor (RF), a protein produced by the immune system that attacks healthy joints. Sara Gaynes Lev, SELF, 30 July 2021

Word History

First Known Use

1949, in the meaning defined above

Time Traveler
The first known use of rheumatoid factor was in 1949

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Cite this Entry

“Rheumatoid factor.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/rheumatoid%20factor. Accessed 9 Sep. 2025.

Medical Definition

rheumatoid factor

noun
: an autoantibody of high molecular weight that reacts against immunoglobulins of the class IgG and is often present in rheumatoid arthritis

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