As a kind of enzymes for diagnostic use. Serum amylase (AMS) is the main type of amylase in serum. It belongs to glycoside chain hydrolase, which is mainly derived from the pancreas. In addition, there are also a small amount of secretion in the proximal duodenum, lung, uterus, and breast during lactation. Amylase plays an important role in the digestion of polysaccharide compounds in food. The determination of serum amylase activity is mainly used for the diagnosis of acute pancreatitis.

Serum amylase can be divided into salivary amylase (S-amylase) and pancreatic amylase (P-amylase). Under normal circumstances, S-amylase and P-amylase account for 60% and 40% of the total serum amylase activity, respectively. In addition to the secretion of S-amylase by the salivary glands, it can also be produced by other organs, such as the lungs, sweat glands, breast, gastrointestinal tract, and genitourinary system. In addition, a small number of malignant tumors can also synthesize and secrete S-amylase. P-amylase is mainly secreted by the pancreas and has certain specificity for the diagnosis of pancreatic diseases.

The most common cause of hyperamylaseemia is pancreatic disease, but there are many causes of hyperamylaseemia, some of which are relatively rare. In the clinical differential diagnosis, non-pancreatic causes should be fully considered to avoid delay in diagnosis and treatment of patients.

1. Pancreatic disease
Acute pancreatitis is the most common cause of hyperamylaseemia, and serum amylase is an important indicator for the diagnosis of acute pancreatitis. Serum amylase activity begins to rise 2-12 hours after the onset of acute pancreatitis, and generally hyperamylaseemia lasts for 3 to 5 days. The elevation of serum amylase is more than 5 times the upper limit of normal, which has high specificity for the diagnosis of acute pancreatitis, but it is only seen in 80%-90% of patients with acute pancreatitis, and the level of amylase in some patients does not reach this height. . The magnitude of the elevation of amylase in patients with acute pancreatitis is not related to the severity of the disease, and non-persistent hyperamylaseemia indicates the occurrence of complications.

2. Acute abdomen

Acute abdominal pain accompanied by hyperamylaseemia is not only found in pancreatic diseases, but also a variety of acute abdomen. The differential diagnosis is particularly important. For example, intestinal obstruction, perforation of gastroduodenal ulcer, mesenteric infarction and rupture of ectopic pregnancy can all lead to increased serum amylase. In most cases, the increase of serum amylase in these diseases is not as obvious as that of acute pancreatitis, and is often lower than normal. The upper limit is 3 times, each disease has corresponding medical history, clinical manifestations and imaging examination results, but there is no morphological change of the pancreas. According to these characteristics, it is not difficult to distinguish it from acute pancreatitis.

3. Malignant tumors
Many malignant tumors can cause elevated serum amylase, the most common are ovarian cancer, lung cancer and multiple myeloma. Ectopic synthesis of tumor tissue is the cause of this phenomenon. After effective treatment, the blood amylase can be significantly reduced, and can rise again after recurrence. This phenomenon not only provides strong evidence for ectopic secretion of tumor tissues, but also indicates that the change of this value in some tumor patients may have the effect of indicating changes in the condition and prognosis.

In addition to lung cancer, ovarian cancer and multiple myeloma, hyperamylaseemia is also seen in gastric cancer, hematological malignancies and breast cancer. The amylase produced by malignant tumors is mostly S-amylase. When hyperamylaseemia occurs clinically and it is difficult to explain pancreatic disease, the detection of amylase isoenzymes is of great value for the differential diagnosis of the cause of hyperamylaseemia.

4. Mumps
Mumps is an acute respiratory infectious disease caused by mumps virus invading the parotid glands. Non-suppurative swelling and pain of the parotid gland are prominent symptoms, and 90% of patients have mild and moderate increases in serum amylase. Hyperamylaseemia caused by mumps is an increase in S-amylase, and the increase in amylase is often proportional to the degree of parotid gland swelling.

Author's Bio: 

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