A 54-year-old man with long history of alcohol abuse and prior history of pancreatitis complains of severe upper abdominal pain and numerous episodes of nonbloody, nonbilious vomiting after a weekend binge of drinking. His serum amylase level is within normal range, but you still suspect acute pancreatitis, knowing that amylase may be falsely depressed in a patient with concomitant:
Helicobacter pylori infection.
Occult gastrointestinal bleeding.
While serum amylase is a reasonable screening tool for acute pancreatitis, it is not perfect. If you can exclude intestinal perforation or infarction from the differential (both of which cause a rise in amylase), then a level >300 U/dL is present in 85% of patients within the first 24 hours of symptoms. Reasons for incorrect normal values include extensive pancreatic necrosis, infarction, and pseudocyst formation. Both serum amylase and serum lipase can be falsely low in patients with hypertriglyceridemia. False lows are also reported in patients with chronic pancreatitis.