This is most diagnostic investigation for acute pancreatitis

The correct option is Serum Lipase.

To understand why serum lipase is the most diagnostic investigation for acute pancreatitis, we can compare its clinical utility with other pancreatic enzymes, particularly serum amylase:
1. Higher Sensitivity and Specificity: Serum lipase is synthesized almost exclusively by pancreatic acinar cells. In contrast, serum amylase is produced by both the pancreas and salivary glands, and its levels can be elevated in various non-pancreatic conditions (such as salivary gland disorders, bowel obstruction, or cholecystitis). Thus, serum lipase is significantly more specific to the pancreas.
2. Longer Half-Life: In acute pancreatitis, both serum amylase and lipase levels rise within 4 to 8 hours of symptom onset. However, serum amylase levels return to normal within 3 to 5 days, whereas serum lipase levels remain elevated for 8 to 14 days. This makes serum lipase much more useful for patients who present late after the onset of abdominal pain.
3. Diagnostic Criteria: According to international guidelines (such as the Atlanta classification), the diagnosis of acute pancreatitis requires at least two of the following three features: clinical abdominal pain, characteristic imaging findings, and pancreatic enzyme levels (lipase or amylase) at least three times the upper limit of normal. Serum lipase is the preferred enzyme due to its superior diagnostic accuracy.