Should You Order Lipase in Suspected Acute Pancreatitis?
Yes, you should order serum lipase when acute pancreatitis is suspected, as it is the preferred single enzyme test with superior diagnostic accuracy compared to amylase. 1
Why Lipase is the Test of Choice
Serum lipase is considered the most reliable diagnostic marker for acute pancreatitis and should be preferred over amylase. 1 The key advantages include:
- Higher sensitivity: Lipase demonstrates 79% sensitivity compared to 72% for amylase in diagnosing acute pancreatitis 1
- Longer diagnostic window: Lipase remains elevated for 8-14 days (rising within 4-8 hours, peaking at 24 hours), while amylase normalizes within 3-7 days 1
- Better late presentation detection: In samples collected 2-3 days after symptom onset, lipase maintains 85% sensitivity with 82% specificity, while amylase drops to only 68% specificity 2
Diagnostic Threshold
Use a cutoff value of three times the upper limit of normal for serum lipase. 1 This threshold:
- Provides optimal diagnostic accuracy with 95% sensitivity and specificity when measured within 0-1 days of symptom onset 2
- Dramatically improves specificity to 98% compared to using the standard upper reference limit 3
- Aligns with the diagnostic criteria requiring lipase >3× upper limit of normal as one of the three diagnostic criteria for acute pancreatitis 4
When Lipase Alone is Sufficient
Do not routinely order both lipase and amylase together, as co-ordering provides minimal additional diagnostic value. 5 The combination:
- Shows little to no increase in diagnostic sensitivity or specificity 5
- Results in unnecessary testing and increased laboratory costs 5
- Only marginally improves specificity from 91% to 98% in late presentations (days 2-3), which rarely changes clinical management 2
Clinical Context Matters
Remember that lipase measurement is part of a diagnostic triad—you need 2 of 3 criteria to diagnose acute pancreatitis: 4
- Abdominal pain consistent with pancreatitis
- Serum lipase >3× upper limit of normal
- Characteristic findings on imaging
Do not rely on clinical assessment alone, as it misclassifies approximately 50% of patients. 4 If clinical suspicion remains high but lipase is not elevated or unavailable, proceed directly to contrast-enhanced CT for definitive diagnosis. 4
Important Caveats
Be aware that lipase can be elevated in non-pancreatic conditions: 1
- Renal disease
- Acute cholecystitis
- Appendicitis
- Bowel obstruction
- Chronic pancreatitis
Lipase cannot determine severity or etiology of acute pancreatitis. 5 For prognostic assessment, use additional markers like CRP ≥150 mg/L at day 3, hematocrit >44%, or procalcitonin. 1
The diagnostic accuracy of lipase decreases significantly after 4-5 days from symptom onset (sensitivity drops to 60%), so imaging becomes more critical for late presentations. 2