Bottom line: Measurements of the pancreatic enzyme, elastase, in the stool can be used to evaluate severe pancreatic exocrine deficiency.
Summary: The secretin/cholecystokinin stimulation test, although rarely used, is still considered the gold standard for detecting pancreatic insufficiency. See summary of pancreatic secretory function tests
Italian consensus guidelines for chronic pancreatitis (Dig Liver Dis. 2010 Nov;42 Suppl 6:S381-406.)
Reports that Fecal elastase-1 test has a high negative predictive value for pancreatic insufficiency, and a good sensitivity in patients with moderate and severe pancreatic failure, but that there is “a lack of data comparing diagnostic power of function tests to new imaging techniques” (S388.)