Lo KC, Sullivan E, Bannen RM, et al. - This study was undertaken to produce a fair, complete profile of serum antibodies against the human proteome, involving the citrullinome and the homocitrullinome, in RA individuals (n = 18), utilizing a high-density peptide array, consisting of > 4.6 million peptides, which retained the whole annotated human proteome. A total of 26 serum samples were profiled on the high-density peptide array. It was found that comprehensive antibody profiling utilizing a high-density peptide array not only recognized novel RA-specific epitopes but also permitted to create a novel diagnostic biomarker that was particular as and more sensitive compared with Abnova cyclic citrullinated peptide 2 assay.