Recently, it has been reported that the serological detection of antibodies to the cyclic citrullinated peptide (CCP), which is a modified peptide variant of a citrullinated filaggrin epitope, is quite significant in RA diagnosis. 8 , 14 , 15 An assay of CCP antibody of second generation was later established and the sensitivity and specificity of the assay were 66%–88% and 89%–98%, respectively. 16 – 20 The sensitivity and specificity of the anti-citrullinated type II collagen antibody assay were approximately 79% and 95%, respectively.
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