Relationship between PABA and Lundh tests: lack of influence of duodenal pH in vivo.

Twenty-five patients with chronic pancreatitis and 25 patients with non-pancreatic abdominal disorders were investigated by Lundh and BT PABA/14C-PABA tests of pancreatic function. The following results emerged: (1) There was a strong positive linear relationship between mean trypsin activity (MTA) and mean chymotrypsin activity (MCA) in duodenal aspirates after a Lundh test meal. (2) There was a strong positive linear relationship between chymotrypsin activity measured with BTEE, or BT PABA as substrate. (3) There was a strong positive correlation between MTA, or MCA, in duodenal juice after a Lundh meal and urinary PABA recovery, or the PABA/14C excretion index (PEI) in patients with chronic pancreatitis, but not in controls. (4) There was no correlation between the pH of duodenal juice in Lundh tests and PABA recovery, or PEI, in patients with or without pancreatic disease. We conclude that the Lundh and BT PABA/14C-PABA tests are equally discriminatory methods of assessing pancreatic exocrine function. The rate limiting effect of pH on BT PABA hydrolysis reported in in-vitro studies does not affect the practical clinical value of the BT PABA/14C-PABA test.