Amylase, isoamylase and macroamylase

Area of Science:

• Biochemistry
• Clinical Diagnostics
• Gastroenterology

Background:

• Hyperamylasaemia is traditionally considered pathognomonic of acute pancreatitis.
• Recent findings indicate other conditions, such as diabetic ketoacidosis, can cause elevated amylase levels.
• The discovery of macroamylase, a complex of amylase and protein, further complicates the interpretation of hyperamylasaemia.

Purpose of the Study:

• To review the diagnostic challenges associated with hyperamylasaemia.
• To discuss the role of macroamylase and amylase clearance to creatinine clearance ratio.
• To evaluate the utility of various enzyme tests in diagnosing pancreatic conditions.

Main Methods:

• Literature review of studies on hyperamylasaemia and acute pancreatitis.
• Analysis of diagnostic criteria and emerging biomarkers.
• Electrophoretic separation of serum amylase isoenzymes.
• Assessment of duodenal juice amylase and other pancreatic function tests.

Main Results:

• Hyperamylasaemia is not exclusive to acute pancreatitis, with diabetic ketoacidosis being a notable exception.
• Macroamylase can lead to falsely elevated serum amylase levels, often with low urine amylase.
• The ratio of amylase clearance to creatinine clearance has been introduced as a diagnostic aid.
• Electrophoretic analysis of amylase isoenzymes has not proven effective at the routine diagnostic level.
• Duodenal juice amylase remains valuable but is now complemented by other enzyme tests for exocrine pancreatic function.

Conclusions:

• The diagnosis of acute pancreatitis based solely on hyperamylasaemia is unreliable.
• Macroamylase and other non-pancreatic causes necessitate careful diagnostic evaluation.
• A combination of biochemical markers and functional tests is crucial for accurate pancreatic assessment.