PARP9 and systemic sclerosis: However, we found a good diagnostic value (AUC > 0.80) to discriminate MCTD from RA and SSc at 17 and 10 CpG sites, respectively, being the highest cg13452062 at IFI44L for RA (AUC = 0.87) and cg22930808 at PARP9 gene for SSc (AUC = 0.85).