PECAM1 and Arthritis: Finally, the logistic regression analysis (data not shown) demonstrated that having baseline GSUS and PDUS scores ≥1.5 at US assessment [OR: 22.93 (95%CI:0.98–534.31)] and CD31+ vessels count ≥24.3 [OR: 23.66 (95%CI: 1.50–373.00)] are two independent factors associated with future achievement of defined arthritis in seronegative UPIA patients (Hosmer-Lemeshowtest: p = 0.35).