Liver Enzymes Presentation

Liver Enzymes Overview

• Focus on enzyme determination methods, clinical significance, and patient preparation.
• Explore tissue sources and specimen considerations for specific enzymes.

Aspartate Aminotransferase (AST)

• Also known as serum glutamic-oxaloacetic transaminase (SGOT).
• Coenzyme: pyridoxal phosphate; key tissue sources include cardiac tissue, liver, and skeletal muscle; minor sources include kidney, pancreas, and erythrocytes.
• Isoenzyme fractions: cytoplasmic (not routinely analyzed) and mitochondrial.

Clinical Significance of AST

• Elevated levels indicate hepatocellular disorders, skeletal muscle involvement, and acute myocardial infarction.
• Highest elevation observed in acute hepatocellular disorders and myocardial infarction, with increases of 5 or more times the upper limit of normal (ULN).
• Additional causes of elevation: circulatory collapse (shock), acute pancreatitis, and infectious mononucleosis.

Specimen Considerations for AST

• Preferred specimen: fresh, un-hemolyzed serum; plasma may also be used.

Alanine Aminotransferase (ALT)

• Known as serum glutamic pyruvic transaminase (SGPT); coenzyme: pyridoxal phosphate.
• Major tissue sources are the liver and kidney, with other sources including heart and skeletal muscle.

Clinical Significance of ALT

• Primarily related to liver diseases; notable exclusions include hepatic cirrhosis and liver neoplasia.
• The De Ritis ratio (AST:ALT) is significant, with a value greater than 1 indicating potential liver issues.
• Highest elevation typically observed in non-alcoholic asymptomatic patients; mild elevations associated with Hepatitis C infection.

Methodologies for ALT Determination

• Wroblewski and La Due method based on specific reactions; also includes alternate methods like Reitman-Frankel and chemiluminescence.

Alkaline Phosphatase (ALP)

• EC code number: 3.1.3.1; essential for various body functions including bone metabolism.
• Major tissue sources include the liver, small intestine, and kidney.

ALP Isoenzymes

• Isoenzymes differentiated using techniques like electrophoresis, heat denaturation, and chemical inhibition.
• Abnormal isoenzyme fractions include Regan, Nagao, and Kasahara, each linked to specific cancers.

Clinical Significance of ALP

• Pronounced elevation (5 or more times ULN) associated with conditions like bile duct obstruction and biliary cirrhosis.
• Moderate elevation (3-5 times ULN) linked to granulomatous liver diseases and metabolic bone diseases.
• Slight elevation up to 3 times ULN tied to viral hepatitis, cirrhosis, and normal growth in children.

Decreased Levels of ALP

• Associated with inherited conditions such as hypophosphatasia or loss of bone isoenzyme.

Specimen and Assay Considerations for ALP

• Avoid hemolysis; timely processing required due to ALP activity increase and interactions with the clot.
• Serum should be prioritized over plasma for accurate measurements.

Assessment Methods for ALP

• Notable methods include Bowers McComb, electrophoresis, heat stability tests, and chemical inhibition techniques.
• Bowers McComb is recognized as the IFCC recommended method with specific substrate and pH requirements.

This quiz explores the various aspects of liver enzymes including their tissue sources, clinical significance, patient preparation, and methods of enzyme determination. Ideal for students in medical laboratory science, it fosters understanding of liver enzyme functions and applications in clinical settings.