Liver Function Test

ALT—location, function, cofactor needed

Mainly hepatocytes; Amino group transfer, role in gluconeogenesis; Requires vitamin B6 (pyridoxal phosphate)

AST—location

Hepatocytes, muscle, heart, intestine

AST:ALT ratio

Normally <1 except alcoholic hepatitis (>2)

ALT/AST elevation meaning

Hepatocyte injury from viruses, toxins, hypoxia

Alkaline phosphatase—location

Canalicular membrane, bile duct epithelium, bone, placenta, intestine, kidney

Alkaline phosphatase elevation—meaning

Elevated in cholestasis, biliary obstruction

GGT—location + meaning

Canalicular membrane, bile duct epithelium, many tissues; Helps confirm hepatic source of elevated AlkPhos

Albumin—source

Synthesized by liver; Poor marker of acute liver injury

Clotting factors—source

Synthesized by liver except VIII and vWF

Clotting factors—vitamin K dependent synthesis in liver

II, VII, IX, X, proteins C and S

INR—meaning + what it measures+caveat

Reflects synthetic function of liver; measures II, VII, and X. INR also elevated in vitamin K deficiency

ANA as a marker

Sensitive but nonspecific autoimmune marker

ASMA

Specific for autoimmune hepatitis

AMA in the evaluation of Liver Disease

Specific for primary biliary cholangitis

Hemochromatosis markers

High ferritin, high transferrin saturation

Wilson disease markers

Low ceruloplasmin, high urinary copper

Alpha‑1 antitrypsin deficiency marker

Low A1AT levels

Clinical signs of liver disease

Scleral icterus, hepatomegaly, spider hemangioma, palmar erthema, gynecomastia, ascites, peripheral edema, JVD, ecchymoses, asterixis, caput medusa, corneal rings

Severe acute hepatocellular injury

Tylenol toxicity, shock liver, DILI, hepatitis A

Moderate hepatocellular injury

Hepatitis B/C, alcoholic hepatitis, MASLD, autoimmune hepatitis, Wilson disease

Mild hepatocellular injury

Choledocholithiasis, hemochromatosis, neoplasia, Gilbert/Dubin‑Johnson/Rotor, cirrhosis

TBili high + normal ALT/AST—first step

Check direct bilirubin

Total Bili high + normal enzymes—direct bili high

Obstruction or conjugation defect

TBili high + normal enzymes—direct bili normal

Hemolysis or Gilbert syndrome

AlkPhos high + normal ALT/AST—next step

Check GGT

AlkPhos high + GGT high

Hepatic source → RUQ ultrasound

AlkPhos high + GGT normal

Non‑hepatic source (bone, placenta)

AlkPhos high + AMA positive

Primary biliary cholangitis

Predominant ALT/AST elevation—viral serologies positive

Viral hepatitis

Predominant ALT/AST elevation—alcohol history

Alcoholic hepatitis

Predominant ALT/AST elevation—drug exposure

DILI

Predominant ALT/AST elevation—ANA/ASMA positive

Autoimmune hepatitis

Predominant ALT/AST elevation—high ferritin/Fe sat

Hemochromatosis

Predominant ALT/AST elevation—obesity/DM

MASLD (fatty liver)