Amylase, an enzyme that changes starch to sugar, is produced in the salivary (parotid) glands and pancreas; much lower activities are present in the ovaries, intestines, and skeletal muscle. If there is an inflammation of the pancreas or salivary glands, much amylase enters the blood. Amylase levels in the urine reflect blood changes by a time lag of 6–10 hours. (See Urine Amylase Excretion and Clearance [Random, Timed Urine, and Blood] in Chapter 3.) Lipase is a glycoprotein that, in the presence of bile salts and colipase, changes fats to fatty acids and glycerol. The pancreas is the major source of this enzyme. Lipase appears in the blood following pancreatic damage at the same time amylase appears (or slightly later) but remains elevated much longer than amylase (7–10 days).

Amylase and lipase tests are used to diagnose and monitor treatment of acute pancreatitis and to differentiate pancreatitis from other acute abdominal disorders (80% of patients with acute pancreatitis will have elevated amylase and lipase levels; lipase stays elevated longer). Lipase assay provides better sensitivity and specificity and is best used with amylase determination.

Amylase:

• Newborns: 6–65 U/L or 0.1–1.1 μkat/L

• Adults: 25–125 U/L or 0.4–2.1 μkat/L

• Older adults (older than 60 years): 24–151 U/L or 0.4–2.5 μkat/L

Lipase:

• Adults: 10–140 U/L or 0.17–2.3 μkat/L

• Older adults (>60 years): 18–180 U/L or 0.30–3.0 μkat/L

Normal values vary widely according to method of testing; check with your laboratory for reference ranges. Amylase levels are low for the first 2 months of life. Most of the activity is of salivary origin. Children up to 2 years of age have virtually no pancreatic amylase.

1. Obtain a 5-mL venous blood sample (red-topped tube). Serum is used. (EDTA, citrate, and oxalate anticoagulant interfere with lipase testing.)

2. Observe standard precautions. Label the specimen with the patient’s name, date and time of collection, and test(s) ordered. Place the specimen in a biohazard bag.

1. Greatly increased amylase levels occur in acute pancreatitis early in the course of the disease. The increase begins 3–6 hours after the onset of pain.

2. Increased amylase levels also occur in the following conditions:

   1. Chronic pancreatitis, pancreatic trauma, pancreatic carcinoma, obstruction of pancreatic duct

   2. Partial gastrectomy

   3. Acute appendicitis, peritonitis

   4. Perforated peptic ulcer

   5. Cerebral trauma, shock

   6. Obstruction or inflammation of salivary duct or gland and mumps

   7. Acute cholecystitis (common duct stone)

   8. Intestinal obstruction with strangulation

   9. Ruptured tubal pregnancy and ectopic pregnancy

   10. Ruptured aortic aneurysm

   11. Macroamylasemia

3. Decreased amylase levels occur in the following conditions:

   1. Pancreatic insufficiency

   2. Hepatitis, severe liver disease

   3. Advanced cystic fibrosis

   4. Pancreatectomy

4. Elevated lipase levels occur in pancreatic disorders (e.g., pancreatitis, alcoholic and nonalcoholic; pancreatic carcinoma).

5. Increased lipase values also are associated with the following conditions:

   1. Cholecystitis

   2. Hemodialysis

   3. Strangulated or infarcted bowel

   4. Peritonitis

   5. Primary biliary cirrhosis

   6. CKD

6. Serum lipase levels are normal in patients with elevated amylase who have peptic ulcer, salivary adenitis, inflammatory bowel disease, intestinal obstruction, and macroamylasemia. Coexistence of increased serum amylase and normal lipase levels may be a helpful clue to the presence of macroamylasemia.

Pretest Patient Care

1. Explain test purpose and procedure. Amylase and lipase testing are done together in the presence of abdominal pain, epigastric tenderness, nausea, and vomiting. These findings characterize acute pancreatitis as well as other acute surgical emergencies.

2. If amylase/creatinine clearance testing is also being done, collect a single, random urine sample at the same time blood is drawn.

3. Follow guidelines in Chapter 1 regarding safe, effective, informed pretest care.