Liver Chemistries - Interpretation of LFTs R-value: Serum (ALT/ULN ALT) / (Alk phos/ULN ALP) • R > 5: Hepatocellular - Check Acute viral hepatitis serologies, HCV RNA • R 2-5: Mixed - Check Acute viral hepatitis serologies, HCV RNA • R < 2: Cholestasis / Obstructive - Check Obtain imaging studies Imperative to Identify Acute Liver Failure (ALF): • Liver injury < 26 weeks • INR > 1.5 • Encephalopathy Cellular Destruction: Hepatocellular Level • AST: Less specific to liver than ALT • ALT: Specific to liver than AST • GGT: - Specific to liver - Assists in liver specificity to elevated ALP • AST/ALT > ALP: Typical of hepatocellular injury • Bilirubin - +/- elevation Obstruction: Cholestasis • ALP - Surface of bile duct epithelia - Cholestasis/Bile salts augment synthesis of ALP - Due to synthesis - rises later - Half life: 1 week • Direct bilirubin: ↑ • AST: ↑ • ALT: ↑ • GGT/5-NT: ↑ • ALP > AST/ALT: typical of cholestatic disease • If ALP ↑: Check GGT & 5-nucleotidase (5-NT) - If both are normal - ALP is from extrahepatic source Production: • Albumin • Coagulation factors: PT/INR Infiltrative - The liver is invaded or replaced by non-hepatic substances, such as neoplasm or amyloid: • Elevation of ALP • Near normal AST/ALT AST:ALT Ratios: • Alcoholic liver disease: > 2 • NASH, Chronic viral hepatitis: < 1 • Cirrhosis: > 1 • Acute muscle injury: > 3 • Chronic muscle injury: ~ 1 Nonhepatic Source of Liver Enzyme Elevation: • Bilirubin: RBC (hemolysis, bleeding, hematoma) • AST: Skeletal muscle, cardiac muscle, RBC, Kidney, Brain • ALT: Skeletal muscle, Cardiac muscle, Kidneys • LDH: Heart, RBC (hemolysis) • ALP: Bone, First trimester placenta, kidneys, intestines, White blood cells Unconjugated Bili > 90% of Total Bili Etiology: • Gilbert's syndrome • Hemolysis #liver #chemistry #diagnosis #differential #Hepatology #transaminitis #LFTs #RValue #interpretation
