A 32 y.o. female presents with elevated liver function tests. AST repeatedly measures high and is currently 215. She also complains of leg weakness.

She has already been evaluated and does not drink alcohol. Hep BS Ag and C Ab are negative. Bilirubin is normal. She does not take medications or herbal supplements. Autoimmune hepatitis has been ruled out with ASMA, ANA, and anti-LKM-1 all negative. A liver biopy was normal. What test needs to be done?