[The PABA test]

Abstract

PABA test has proved to be an easy and reliable test for determination of exocrine pancreatic insufficiency. N-benzoyl-L-tyrosyl-p-aminobenzoic acid or 4-(N-acetyl-L-tyrosyl) aminobenzoic acid are split by action of chymotrypsin in the small intestine. N.O-diacetyl-L-tyrosyl-p-aminobenzoic acid is converted easy in vivo in 4(N-acetyl-L-tyrosyl) aminobenzoic acid. The amount of 4-aminobenzoic acid (PABA) in urine collected for 6-10 hours is used as an index of chymotrypsin production. The concentration of PABA (and aromatic amines) is estimated in urine by the Bratton and Marshall method. p-dimethylamino cinnamaldehyde is less useful for the determination of urinary PABA. 60 min are necessary as time for acid hydrolysis of conjugated PABA metabolites. False abnormal test results are found for instance in patients with inflammatory bowel diseases, small bowel resection, impaired liver function, anorexia nervosa, lambliasis or renal insufficiency. The PABA test appears in consideration of these restrictions to be an useful simple method in the assessment of exocrine pancreatic function.