False positive rheumatoid factor can be associated With all except-
Correct Answer: Inflammatory bowel disease
Description: Rheumatoid factor: Antibodies in rheumatoid disease, especially the IgM, can be demonstrated by the Rose Waaler test, latex fixation test or bentonite flocculation. Rheumatoid factor is positive in 80% of adults with rheumatoid ahritis. A differential agglutination titer of16 and above is diagnostic of rheumatoid ahritis. Patients with systemic inflammatory diseases such as RA will often present with elevated nonspecific inflammatory markers such as an ESR or CRP. Detection of serum RF and anti-CCP antibodies is impoant in differentiating RA from other polyaicular diseases, although RF lacks diagnostic specificity and may be found in association with other chronic inflammatory diseases in which ahritis figures in the clinical manifestations.IgM, IgG, and IgA isotypes of RF occur in sera from patients withRA, although the IgM isotype is the one most frequently measured by commercial laboratories. Serum IgM RF has been found in 75-80% ofpatients with RA; therefore, a negative result does not exclude the presence of this disease. It is also found in other connective tissue diseases,such as primary Sjogren's syndrome, systemic lupus erythematosus,and type II mixed essential cryoglobulinemia, as well as chronic infections such as subacute bacterial endocarditis and hepatitis B and C.Serum RF may also be detected in 1-5% of the healthy population.The presence of serum anti-CCP antibodies has about the same sensitivity as serum RF for the diagnosis of RA. However, its diagnostic specificity approaches 95%, so a positive test for anti-CCP antibodies inthe setting of an early inflammatory ahritis is useful for distinguishing RA from other forms of ahritis. There is some incremental value intesting for the presence of both RF and anti-CCP, as some patients withRA are positive for RF but negative for anti-CCP and vice versa. The presence of RF or anti-CCP antibodies also has prognostic significance, with anti-CCP antibodies showing the most value for predicting worse outcomes . Ref - harrisons 20e p2535
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