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Amylase, Pancreatic
(Pancreatic α-Amylase – Pancreas-Specific Digestive Enzyme)
Synonyms
- Pancreatic amylase
- P-AMY
- P-type amylase
- α-Amylase (pancreatic isoenzyme)
- EC 3.2.1.1 (pancreatic isoform)
Units of Measurement
nkat/L, µkat/L, nmol/(s•L), µmol/(s•L), U/L, IU/L, µmol/(min•L), µmol/(h•L), µmol/(h•mL)
Description
Pancreatic Amylase (P-AMY) is the pancreas-specific isoenzyme of total amylase.
It is produced by acinar cells of the pancreas and secreted into the duodenum to digest carbohydrates.
P-AMY is more specific for pancreatic injury than total amylase because it excludes the salivary isoenzyme.
P-AMY is used to evaluate:
- Acute pancreatitis
- Pancreatic duct obstruction
- Pancreatic trauma
- Chronic pancreatitis (during acute flare-ups)
- Post-ERCP pancreatitis
- Pancreatic tumors
Physiological Role
- Hydrolyzes starch → maltose + dextrins
- Works optimally at pH 6.7–7.0
- Released into bloodstream when acinar cells are injured
Clinical Significance
Increased Pancreatic Amylase
1. Acute Pancreatitis (Most Important)
- Rises within 3–6 hours of onset
- Peaks at 24 hours
- Returns to normal in 3–5 days
- More pancreas-specific than total amylase
2. Pancreatic Duct Obstruction
- Gallstones
- Pancreatic carcinoma
- Chronic pancreatitis with strictures
- Post-ERCP injury
3. Other Pancreatic Causes
- Pancreatic trauma
- Pseudocyst formation
- Pancreatic divisum
4. Non-Pancreatic Causes (rare)
- Renal failure (reduced clearance)
- Macroamylasemia (rare for P-AMY)
Decreased Pancreatic Amylase
Seen in:
- Chronic pancreatitis (loss of acinar cells)
- Cystic fibrosis
- Advanced pancreatic cancer
- Pancreatic necrosis
Low levels suggest pancreatic insufficiency when combined with low lipase or fecal elastase.
Reference Intervals
(Tietz 8E + Mayo Clinic + IFCC)
Reference ranges vary by analyzer, reagent, and temperature (37°C).
Adult Pancreatic Amylase (Serum)
- 13 – 53 U/L
- SI: 0.22 – 0.88 µkat/L
(Using conversion: 1 U/L = 16.67 nkat/L)
Total Amylase for comparison
- 30 – 110 U/L
Urine P-AMY
- Not commonly measured (total amylase used instead)
Pancreatitis Diagnostic Notes
- Pancreatic amylase + lipase together improve diagnostic accuracy.
- Lipase remains elevated longer and is more specific.
- P-AMY normal does not rule out pancreatitis (especially late presentations).
Unit Meanings
| Unit | Meaning |
| nkat/L | nanokatal per liter |
| µkat/L | microkatal per liter |
| nmol/(s•L) | nanomole per second per liter |
| µmol/(s•L) | micromole per second per liter |
| U/L | enzyme units per liter |
| IU/L | international units per liter |
| µmol/(min•L) | micromoles per minute per liter |
| µmol/(h•L) | micromoles per hour per liter |
| µmol/(h•mL) | micromoles per hour per millilite |
Time conversions
- µmol/(min•L) × 60 = µmol/(h•L)
- µmol/(h•L) ÷ 1000 = µmol/(h•mL)
Isoenzyme Interpretation
P-AMY helps differentiate:
| Condition | P-AMY | S-AMY |
| Acute pancreatitis | ↑↑↑ | Slight ↑ |
| Parotitis | Normal | ↑↑ |
| Macroamylasemia | Normal/slightly ↑ | Normal/slightly ↑ |
| Renal failure | ↑ | ↑ |
Analytical Notes
- Preferred sample: serum
- Hemolysis: minimal interference
- Lipemic samples may interfere with total amylase, but less effect on isoamylase
- Isoamylase fractionation is done via:
- Electrophoresis
- Chromatography
- Immunoinhibition
- Electrophoresis
Clinical Pearls
- P-AMY is more pancreas-specific than total amylase but less specific than lipase.
- Best used for early detection of acute pancreatitis.
- Chronic pancreatitis may show low P-AMY due to acinar cell loss.
- P-AMY > 3× ULN strongly suggests pancreatic origin.
- Normal P-AMY with high total amylase → salivary source or macroamylasemia.
Interesting Fact
Pancreatic amylase has a slightly different structure from salivary amylase, allowing analytical methods to selectively inhibit one isozyme while measuring the other.
References
- Tietz Clinical Chemistry and Molecular Diagnostics, 8th Edition - Enzymes & Pancreatic Markers.
- IFCC Enzyme Standardization Guidelines.
- Mayo Clinic Laboratories - Pancreatic Amylase Test.
- ARUP Consult - Pancreatic Function Testing.
- ACG/AGA Guidelines - Acute Pancreatitis Diagnosis.
- NIH / MedlinePlus - Pancreatic Enzymes.