Amylase Serum

What sample is needed for an Amylase Serum?

1. This test is done in the patient’s serum.
2. The serum is stable at room temperature for 7 days and at 4 °C for one month.
3. How to get good serum?
4. Take 3 to 5 ml of blood in a disposable syringe or vacutainer. Keep the syringe for 15 to 30 minutes and then centrifuge for 2 to 4 minutes. This will yield a clear serum.

What are the precautions for Amylase Serum?

1. Avoid alcohol intake before sampling because it gives rise to an increase in the amylase level.
2. Urine can be collected at 2 hours or 24 hours sample. Refrigerate the urine.
3. Avoid contamination with saliva.
4. Lipemia interferes with the reading of the result.
5. Anticoagulant EDTA, fluoride, oxalate, and citrate decreased amylase levels. These anticoagulants bind the calcium ions.

What are the Indications for Amylase Serum?

1. Diagnosing acute pancreatitis and monitoring the treatment are also important.
2. To differentiate other abdominal pain, epigastric discomfort, nausea, and vomiting.
3. In the case of ascites, it may be done to rule out pancreatitis.

How will you classify amylase?

1. Serum Amylase primarily consists of salivary gland (S-type) and pancreas (p-type) isoenzymes.
2. Amylase exists in two isoenzyme forms:
   1. P – amylase is 40% of the total and is found in the pancreas.
   2. S – amylase is 60% of the total and is found in the salivary glands, ovary, fallopian tubes, bronchial epithelium, testes, and intestine.
3. α-Amylase is found in humans.
4. β-Amylase is found in bacteria and plants.
   1. Both types may increase in renal insufficiency.

How does Amylase synthesis take place?

1. Amylase is the smallest enzyme, with a molecular weight of 50,000 to 55,000.
   1. Because of its small size, it is filtered through the glomeruli and appears in the urine.
2. This enzyme is synthesized in the pancreas and salivary glands. Amylase is secreted into the gastrointestinal tract, which helps digest starch and glycogen in the mouth, stomach, and intestine.
   1. Serum amylase consists of:
      1. Salivary gland amylase is  S-type.
      2. Pancreatic amylase is P-type.

3. Amylase is normally secreted from the pancreatic acinar cells into the pancreatic duct and delivered to the duodenum.
4. Once in the intestine, it helps catabolize carbohydrates and starch to simple sugars.

5. Amylase activity is low in infants’ blood for the first two months of life and reaches the adult level by one year.
6. Amylase high activity is seen in the Pancreas and parotid gland.
7. Once pancreatic acinar cells are damaged, amylase outpours into the peritoneum and is absorbed by the blood and lymph.

What is the clinical significance of Amylase Serum?

1. Amylase activity in the blood is low and constant, increasing in acute pancreatitis and salivary gland inflammations.
2. Its main clinical significance is in the following:
3. P-amylase is raised in Pancreatic lesions like:
   1. Acute pancreatitis.
   2. Biliary tract diseases like cholecystitis give rise to an increase up to 4 times the normal.
   3. It is raised in the intraabdominal lesion and may be 4 times the normal value.
   4. Acute appendicitis and peritonitis slightly increase P-amylase; this may be 2 to 3 times the normal.
   5. In renal insufficiency, P-amylase is increased according to the renal lesion and is usually not >5 times the normal.
   6. Amylase may be increased in neoplastic diseases and may be high, up to 50 times the normal.
4. S-amylase is raised in salivary gland lesions like:
   1. Infections of the salivary glands.
   2. Radiation of the salivary glands.
   3. If there is an obstruction to the drainage.
   4. After the surgery on the salivary glands.
   5. Tumors of the salivary glands.
5. It is found to be raised in 80% of diabetic ketoacidosis cases.
6. 10% of alcoholics with alcoholic intoxication may raise levels to 3 times the normal.
7. Some drugs may give rise to hyperamylasemia.

What is the serum amylase level in acute pancreatitis?

1. Amylase increases in the first 3 to 6 hours (another reference for 2 to 12 hours) after the onset of the symptoms.
2. The maximum level (peak) is 20 to  30 hours (another reference is 12 to 72 hours).
3. It falls to normal within 48 to 72 hours (3 to 5 days).
4. It may increase to 40 times normal; the level may vary from 250 to 1000 Somogyi units/dL.
   1. The level may go much higher than the above value.
5. In case of a persistent level of more than 5 days, it suggests a complication like a pseudocyst.

What is the normal Amylase level?

The value may vary from lab to lab.

• Adult = 30 to 220 U/L.
• Newborn = 6 to 65 U /L

Another source:

• Newborn   =  5 to 65 U/L
• Adult        =  27 to 131 U/L
• Adult 60 to 90 years  = 24 to 151 U/L

Source 2

• Serum
  • Adult = 60 to 120 Somogyi unit/dL
  • Values may increase during pregnancy.
  • Values may increase in older adults.
• Urine 24 hours
  • Up to 5000 Somogyi units/24 hours

Another source:

• Amylase serum = 25 to 130 U/L
• Amylase urine = 1 to 15 U/L
  • Conversion factor = Somogyi unit to International unit = 1.85

What are the Critical values of serum amylase?

• More than three times the upper limit of the normal.
• >200 U/L.

How will you diagnose Acute Pancreatitis?

1. Serum amylase level rise starts in  2 to 12 hours.
   1. The peak level is reached in 12 to 72 hours.
2. The normal level reaches 3 to 4 days.
   1. 10% of the cases of acute pancreatitis are associated with a normal level of amylase.
   2. Sensitivity is lowest in chronic relapsing and alcoholic pancreatitis.
3. For diagnosis of acute pancreatitis:
   1. Amylase is 3 times the normal with a specificity of 95% and sensitivity of 60 to 80%.
   2. There is an increase in the pancreatic isoenzymes of amylase (also increased in the pancreatic pseudocyst).
   3. The salivary type of amylase is found in esophageal rupture, peptic ulcer, necrosis of the small intestine, and 10% of metastatic cancer.
   4. Lipase is also 3 times the normal, with a specificity and sensitivity of 90% each.
4. The pleural fluid/serum amylase ratio may be normal early and increase over time.
5. 30% of the cases are due to non-pancreatic causes like:
   1. Diabetic ketoacidosis.
   2. Acute cholecystitis.
   3. Peptic ulcers.
   4. Salpingitis.
   5. Ectopic pregnancy.
   6. Intestinal ischemia.
   7. Intestinal obstruction.
   8. Renal insufficiency.
   9. Macromylasemia.

What is the importance of Ranson criteria for the prognosis and mortality of acute pancreatitis?

• These points are added based on the following clinical and laboratory findings.

How will you interpret Ranson criteria?

1. A score of 3 or 4 indicates severe acute pancreatitis.
2. The scoring in ICU was applied within 24 hours of admission.
3. Some of the ICUs advise more tests and parameters like:
   1. paO2 = <60 mm Hg at 48 hours.
   2. Base deficit = >4 meq/L at 48 hours.
   3. Fluid sequestration = >6L at 48 hours.

What is the significance of the Amylase: creatinine (A/Cr) clearance ratio?

1. This test can be done on a random sample of blood and urine. There is no need to collect 24-hour urine samples.
2. Amylase secretion by the kidneys depends upon renal functions.
3. Amylase urinary excretion correlates with creatinine clearance.

4. A/Cr becomes abnormal 1 to 2 days after the elevation of the serum amylase, but it remains abnormal for about as long as urinary amylase.
5. Some people believe 90% sensitivity for acute pancreatitis.
6. A/Cr is more specific for pancreatitis than changes in the serum amylase level.

What are the causes of increased serum Amylase?

1. Acute Pancreatitis and Acute exacerbation of chronic Pancreatitis.
2. Pancreatic cyst and pseudocyst.
3. Acute alcoholic poisoning.
4. Salivary gland diseases like mumps, duct obstruction, or parotitis.
5. Maybe in acute cholecystitis or intestinal obstructions.
6. Increased obstruction of the common bile duct, pancreatic duct, or ampulla of Vater.
7. Ruptured Ectopic Pregnancy.
8. Renal failure due to reduced excretion by the kidneys.
9. Diabetic ketoacidosis.
10. In peritonitis.
11. In some of the lungs and ovarian tumors.
12. Alcohol intake.
13. It may be seen in abdominal trauma, head injury, viral infections, and postoperative patients.

What are the causes of decreased serum amylase?

1. Extensive marked destruction of the pancreas, e.g., Acute Fulminant Pancreatitis.
2. Chronic Pancreatitis and Pancreatic Cancer.
3. In pancreatectomy.
4. Cirrhosis and severe liver diseases like hepatitis.
5. Perforating or penetrating peptic ulcers.
6. Toxemia of pregnancy.
7. Advanced cystic fibrosis.

What are the causes of normal serum Amylase?

1. Relapsing chronic pancreatitis.
2. Frequently normal in acute alcoholic pancreatitis.
3. Technical problem in case of hypertriglyceridemia. It interferes with the estimation.

What are the Important facts about serum amylase?

• An elevated serum amylase level is not a specific test because a disorder other than the pancreas produces amylase elevation.

Questions and answers: