Which of the following is the most sensitive serum marker for acute pancreatitis in the first 24 hours of symptom onset?

Explanation

## Serum Markers in Acute Pancreatitis **Key Point:** Serum lipase is the most sensitive and specific marker for acute pancreatitis, particularly within the first 24 hours of symptom onset. ### Comparison of Markers | Marker | Sensitivity | Specificity | Time to Rise | Time to Peak | Duration | |--------|-------------|-------------|--------------|--------------|----------| | **Serum Lipase** | 85–100% | 95–99% | 4–8 hours | 24–72 hours | 8–14 days | | **Serum Amylase** | 75–90% | 85–98% | 2–6 hours | 24–48 hours | 3–5 days | | **Procalcitonin** | 60–80% | Variable | 6–12 hours | 48–72 hours | Longer | | **CRP** | 70–90% | Low | 12–24 hours | 48–72 hours | Prolonged | **High-Yield:** Lipase remains elevated for 8–14 days, making it superior to amylase (which normalizes in 3–5 days) for late presentation cases. **Clinical Pearl:** A lipase level >3× the upper limit of normal (ULN) in the presence of characteristic abdominal pain and imaging findings is diagnostic of acute pancreatitis [cite:Harrison 21e Ch 297]. **Warning:** Amylase is NOT more sensitive than lipase. Although amylase rises slightly faster (2–6 hours vs. 4–8 hours), lipase has superior overall sensitivity and specificity, especially in the critical first 24 hours. ### Why Lipase is Preferred 1. **Higher specificity** — amylase can be elevated in salivary gland disease, bowel perforation, and other conditions 2. **Longer window of detection** — remains elevated longer, useful in delayed presentations 3. **Better correlation with severity** — lipase levels correlate more closely with pancreatic necrosis and organ failure 4. **Pancreas-specific isoenzyme** — lipase is produced almost exclusively by the pancreas