My alt/ast enzymes are elevated and i tested positive for mitochondrial m2 ab igg (34.6) antibodies. is this a definitive diagnosis of pbc?

No: What's the titer? Does this match your symptoms / signs / other labs? Even the big fancy commercial labs make mistakes with these.

False +ve AMA <2%: At higher level of AP, PBC can be diagnosed without a liver biopsy provided that the antimitochondrial antibody (AMA) is positive. Patients with high AP and high aspartate aminotransferase (AST) levels should undergo a liver biopsy to diagnose the overlap of autoimmune hepatitis with PBC.Anti-mitochondrial M2 antibodyis specific for PBC, but can also be found in Auto-immune hepatitis.