The serum levels of PAI-1, uPA, and suPAR were measured using ELISA, and the diagnostic performance of two widely debated suPAR ELISA kits, i.e., Human suPAR ELISA (Biovendor R&D, Brno, Czech Republic) and suPARnostic ELISA (Virogates, Copenaghen, Denmark), was examined in patients with SSc and in healthy controls. The gene discussed is SERPINE1; the disease is systemic sclerosis.