Rheumatoid factors a source of non-specificity in enzyme immunoassays

Rheumatoid factors a source of non-specificity in enzyme immunoassays Most rheumatoid arthritis patients, but also 

These RF are often heterogeneous, but may become virtually monoclonal after a prolonged illness. It is not uncommon to find RF in hyperimmune sera. Their role is not clear, but they may clear the plasma of circulating immune complexes. 

The anti-IgG nature of RF and the high detectability of ElA may be responsible for high background reactions in sandwich methods (Section 14.2.2) which, however, can be reduced to insignificant levels using different methods (Section 14.5.2). 

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