A 62-year-old asymptomatic man is found to have serum amylase of 480 U/L on three separate occasions over six months. Serum lipase is normal, abdominal imaging shows a normal pancreas, and he is entirely well. Which single test result would best confirm the underlying diagnosis?
- A Urinary amylase excretion within the normal range ✓
- B Urinary amylase excretion markedly elevated above normal
- C Elevated serum C-reactive protein
- D Low serum immunoglobulin A level
Correct answer: A. Urinary amylase excretion within the normal range
Explanation
The picture suggests macroamylasemia, in which amylase forms complexes with immunoglobulin (usually IgG) that are too large for glomerular filtration. Serum amylase therefore rises while urinary amylase remains normal because the macrocomplex cannot be excreted. In true pancreatitis both serum and urinary amylase are elevated, since filtered amylase appears in urine. Normal lipase and a well patient further argue against pancreatic disease. Confirmation can be obtained by demonstrating the complex on gel filtration or precipitation studies.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.