PABA screening test for exocrine pancreatic function in infants and children.

P-Amino-benzoic acid (PABA) is split specifically by pancreatic chymotrypsin from the synthetic tripeptide N-benzoyl-L-tyrosyl-PABA. The urinary excretion of absorbed PABA serves as an index for exocrine pancreatic function. The peptide (0.015 g/kg) was administered orally to 20 controls (aged between 5 months and 16 years), 6 patients with exocrine pancreatic insufficiency caused by cystic fibrosis (CF), and 9 newborn infants. In the controls the mean 6-hour PABA recovery was 58.5% (+/- 11.2 SD). Recovery in patients with CF was lower (P less than 0.001) with no overlap. In newborn infants the mean 6-hour PABA recovery was 23.4 (+/- 17.7 SD); overlapping in 3 instances with the results in CF patients. This simple, noninvasive test thus appears promising and merits further investigation in younger infants, especially newborns.