The utility of PR3-ANCA to aid in the diagnosis of PSC was compared to aANCA detected by IIF, while the diagnostic specificity of these assays was assessed in PSC and compared to other liver diseases including those of autoimmune etiology [primary biliary cirrhosis (PBC), autoimmune hepatitis (AIH) and overlap syndromes of AIH-PBC, AIH-PSC]. Here, PRTN3 is linked to primary biliary cholangitis.