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Amylase
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A starch-digesting enzyme from the pancreas (P-type) and salivary glands (S-type). It rises early in acute pancreatitis but is less specific than lipase, and is now a second-line test.
Reference interval
| Conventional (U/L) | SI (U/L) | |
|---|---|---|
| Adults | 30–110 U/L | 30–110 U/L |
Specimen: Serum or heparinised plasma (urine for ratio studies) · Conventional × 1 = SI
Causes of high values
Acute pancreatitis (often more than 3 times the upper limit), chronic pancreatitis flare, salivary gland disease (mumps, stones), bowel obstruction or perforation, mesenteric ischaemia, ectopic pregnancy, renal failure, macroamylasaemia, diabetic ketoacidosis.
Causes of low values
Extensive pancreatic destruction (chronic pancreatitis, pancreatectomy), cystic fibrosis, hypertriglyceridaemia-induced pancreatitis can give a falsely low value through interference.
Pre-analytical and method notes
Values depend on the method and substrate, and some laboratories use an upper limit of about 100 to 125 U/L. Pancreatic isoamylase is more specific, amylase returns to normal within 3 to 5 days, and the height of the rise does not correlate with severity. Reference intervals vary by laboratory, method and population; use the interval printed on the report.
References
- Rifai N, Horvath AR, Wittwer CT. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. Elsevier, 6th edition (2018) — Tier 3 (textbook)
- McPherson RA, Pincus MR. Henry's Clinical Diagnosis and Management by Laboratory Methods. Elsevier — Tier 3 (textbook)
- Sleisenger and Fordtran's Gastrointestinal and Liver Disease. Elsevier, 11th edition (2020) — Tier 3 (textbook)
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