The most appropriate test to confirm a clinical diagnosis of early chronic pancreatitis is which of the following?

d. Endoscopic retrograde cholangiopancreatography

Routine tests of blood or serum are not helpful in making a diagnosis of chronic pancreatitis. Although serum amylase levels are almost always elevated in acute pancreatitis—amylase levels may be normal, elevated, or subnormal in chronic pancreatitis. Determination of urinary amylase secretion and calculation of urinary amylase clearance does not improve sensitivity or specificity. Indirect tests of pancreatic function which measure absorption of nutrients that first require pancreatic digestion are not helpful in early cases of chronic pancreatitis. Clinically detectable malabsorption is absent until 90% of exocrine function is lost. Because of this, indirect tests of pancreatic function do not detect early disease. In addition, false positive tests may occur in other disease states associated with malabsorption (Crohn’s disease, sprue, postgastrectomy states, or in association with diabetes mellitus, cirrhosis, or renal disease. ERCP has become widely recognized as the most sensitive and reliable method for diagnosing chronic pancreatitis. Sensitivity approaches 90% with equal specificity.