50 Amylase

Amylase: pancreatic and salivary enzyme, acute pancreatitis criteria and other causes of raised amylase.

Amylase is an enzyme that breaks down starch and other complex carbohydrates into simpler sugars. It is produced mainly by the pancreas (P-type) and the salivary glands (S-type). Salivary amylase starts digesting starch in the mouth; pancreatic amylase continues in the small intestine. Normally only a small amount enters the blood and is excreted by the kidneys. When the pancreas is inflamed, amylase leaks into the blood and its level rises sharply, which makes it a classic test for acute pancreatitis.

PancreasEnzymesAcute pancreatitis

Serum, typical range≈ 30–110 U/L (lab-dependent)

Acute pancreatitis≥ 3 × upper limit

Better testlipase

Returns to normalwithin a few days

Figure 1. Serum amylase zones expressed as multiples of the laboratory upper reference limit (ULN).

Diagnosis of acute pancreatitis

According to the revised Atlanta classification, acute pancreatitis is diagnosed when two of three criteria are present: typical abdominal pain (persistent, severe, upper abdominal, often radiating to the back); lipase or amylase at least three times the upper limit of normal; and typical findings on imaging. Lipase is more sensitive and specific than amylase and stays raised longer. The height of the enzyme level does not reflect the severity of pancreatitis.

Other causes of raised amylase

Salivary gland disease: mumps, parotitis, salivary stones
Other abdominal emergencies: perforated ulcer, bowel obstruction or ischaemia, ruptured ectopic pregnancy, acute cholecystitis
Reduced clearance: kidney failure; macroamylasaemia (amylase bound to antibodies, harmless)
Alcohol use, diabetic ketoacidosis, some tumours, after ERCP

Low amylase may occur in chronic pancreatitis with loss of pancreatic tissue and in cystic fibrosis.

Seek emergency care

for severe upper abdominal pain radiating to the back, especially with vomiting, fever, jaundice or after heavy alcohol intake.

References

Banks PA, Bollen TL, Dervenis C, et al. Classification of acute pancreatitis—2012: revision of the Atlanta classification and definitions by international consensus. Gut. 2013;62(1):102–111. doi:10.1136/gutjnl-2012-302779

This article is for general information and does not replace a consultation with a doctor. Laboratory results must be interpreted by a physician together with symptoms and other tests.

Published on 27 April 2024