Amylase

What is being analysed?
This test measures the amount of amylase in the blood or urine. Amylase is one of the enzymes produced by the pancreas that are involved in the digestion of fats, proteins and carbohydrates. It reaches the duodenum through the pancreatic duct, where it helps digest dietary carbohydrates. Amylase is also produced by other organs, particularly the salivary glands.

Normally only small amounts of amylase are present in the blood and urine. When pancreatic cells are damaged (as in pancreatitis) or the pancreatic duct is blocked (by stones or, rarely, pancreatic cancer), more amylase enters the circulation, so its level rises in the blood and in the urine, through which it is excreted.

How is it used?
Blood amylase is requested, often together with blood lipase, to confirm the diagnosis of and monitor acute or chronic pancreatitis (inflammation of the pancreas) and other diseases affecting the pancreas. Urine amylase may also be requested. The urine level usually reflects the blood level, but it rises and falls later. Sometimes creatinine clearance is requested together with urine amylase to assess kidney function, since reduced kidney function lowers the amount of amylase excreted.

Amylase is sometimes used to monitor the treatment of cancers affecting the pancreas and after the removal of stones following biliary colic.

When is it requested?
Blood amylase may be requested when there are symptoms that may involve the pancreas, such as severe abdominal pain, fever, loss of appetite or nausea. Urine amylase may be requested with or after blood amylase. One or both may also be requested to monitor the effectiveness of treatment and changes in levels over time.

What does the test result mean?
In acute pancreatitis, blood amylase levels rise (often to 4-6 times the upper reference limit). The rise occurs within 12 hours of the damage to the pancreas, and levels stay high until the cause has been removed; they then return to normal within a few days. In chronic pancreatitis amylase levels are initially moderately raised but often fall over time as the pancreas is progressively damaged.

Amylase levels can rise significantly with blockage of the pancreatic duct, pancreatic cancer and biliary colic. Urine and blood amylase levels can also rise in a variety of other conditions such as ovarian and lung cancer, ectopic pregnancy, mumps, bowel obstruction or a perforated ulcer, but these conditions are not generally diagnosed or monitored with amylase. Low blood and urine levels may indicate permanent damage to the amylase-producing cells of the pancreas. Raised blood levels with low urine levels suggest impaired kidney function or macroamylasaemia, a benign condition in which amylase forms a complex with other proteins in the blood.

Since the reference values for amylase vary from laboratory to laboratory depending on the method used, there is no universally accepted normal or high value.

Is there anything else I should know?
In acute pancreatitis, high amylase levels change in parallel with lipase levels, although lipase takes longer to rise and stays high longer than amylase.

Chronic pancreatitis is often associated with alcoholism. It can be caused by injury or by blockage of the pancreatic duct and can be associated with genetic abnormalities such as cystic fibrosis.
In chronic pancreatitis amylase levels may initially be moderately raised but often fall over time as the pancreas is progressively damaged.

1. Can medication affect amylase levels?
2. Can amylase be measured at home?
3. What is the difference between P-amylase and S-amylase?

1. Can medication affect amylase levels?
Yes. Some medicines can raise amylase levels: aspirin, diuretics, oral contraceptives, corticosteroids, indometacin, ethyl alcohol and opiates.

2. Can amylase be measured at home?
No. It is not a difficult test, but it requires specialised equipment. It is performed in laboratories and some doctors’ surgeries

3. What is the difference between P-amylase and S-amylase?
Amylase is an enzyme with several isoenzymes. Different tissues produce different forms. P-amylase refers to amylase produced mainly in the pancreas. S-amylase refers to amylase produced mainly in the salivary glands.
P-amylase levels rise with damage to or inflammation of the pancreas.
S-amylase levels rise with damage to or inflammation of the salivary glands.