Investigation of serum biomarkers in Rheumatoid and Psoriatic arthritis patients for disease-specific signatures

Background Rheumatoid arthritis (RA) and Psoriatic arthritis (PsA) are systemic auto-immune disease of unknown aetiology that leads to systemic inflammation and synovial joint destruction. Identification of specific serum proteins that selectively regulate these diseases, or which precede disease development could have great potential as disease biomarkers and predictors. Methods Serum level of C-reactive protein (CRP), sICAM-1, sVCAM-1, Serum amyloid A (SAA), Matrix metalloproteinases (MMPs 1,3 and 9) and metabolic markers: Active Glucose-dependent Insulinotropic polypeptide (GIP), active Glucagon-like peptide-1 (GLP-1), C-Peptide, Glucagon, Insulin, Leptin, Pancreatic Polypeptide (PP) were measured by multiplex analysis by MSD assay. Results Serum level of sICAM-1, MMP1, MMP3, PP, c-Peptide, CRP and SAA were specifically upregulated in RA, but not in PsA disease, displaying high sensitivity (ROC curves), thus making them suitable markers for discriminating RA from PsA patients, especially in the early phase of the diseases. Differences in gender, BMI, and disease activity were observed. This is the first study which directly compare serum metabolic markers between diseases and identify specific disease signatures between RA and PsA. In addition, this study, identified that CRP, SAA, GLP-1, GIP-1, Leptin and PP serum protein precede disease onset, as are already altered in the serum of ‘individual at risk’ of developing RA. Of these CRP, SAA, Leptin and PP might predicted IAR conversion to RA+, thus making them suitable candidate for disease prediction. Conclusions Altogether, this study identifies selective serum marker associated with RA and PsA, which are pathotype-specific and are predictor of RA disease onset.