Diagnostic Use
There are 2 forms of amylase: P-amylase is specific for the pancreas as tissue of origin. S-amylase can originate from many organs, including salivary and parotid glands, breast, amniotic fluid, lungs, testes and fallopian tubes, as well as neoplasms (including pancreatic cancer).
Total amylase measures both S and P-amylase forms.
If “amylase” is requested, total amylase will be performed.
A specific assay for P-amylase is available either as a standalone test or together with total amylase. P-amylase needs to be specifically requested or test added within 6 days of collection. P-amylase is no longer automatically performed on all raised total amylase results.
Interpretation
In acute pancreatitis, levels peak early and decline over 3 to 4 days. For diagnosis of acute pancreatitis both the amylase level (typically 3 or 4 times greater than normal) and its time-course in relation to the abdominal pain are important. Prolonged elevation of amylase may be due to pancreatic pseudocyst formation.
Total amylase can be increased in many acute abdominal disorders including perforated peptic ulcer, acute cholecystitis, intestinal obstruction, trauma, and ectopic pregnancy.
Elevated amylase can also occur in diabetic ketoacidosis and renal failure (failure to clear the enzyme).
Ectopic pregnancy and salivary gland disorders (parotitis, mumps) cause increased total amylase, with normal P-amylase levels.
Macroamylasaemia is a cause of chronically elevated serum amylase levels, due to complexing of amylase to large proteins and reduced clearance by renal filtration. This is an incidental finding and has no clinical effects. Macroamylasaemia can be differentiated from a true raised amylase by
(a) lipase measurement
(b) PEG precipitation of serum followed by repeat amylase assay (PEG precipates macroamylase but not normal amylase). Contact the on-call chemical pathologist if you require this test.
(b) measuring urinary amylase, which is high in cases of true raised amylase and low in macroamylasemia.
Reference Intervals
Units: U/L
Reference intervals:
Plasma amylase (total) : 28 – 100
Pancreatic amylase : 8 – 53
Test Method
Principle: Enzymatic/Colorimetric
Reagents: Roche P amylase kit
Analyser: Cobas c502
Uncertainty of Measurement
Uncertainty of measurement: 5%