GCG and rheumatoid arthritis: Interestingly, CRP, SAA, GLP-1 and GIP-1 fully overlapped between RA and PsA, thus making them strong candidate markers for both diseases, whereas sICAM-1, MMP1, MMP3, PP and c-Peptide were exclusively significant in RA, thus suggesting that they may be more unique as RA biomarkers.