Failure of p‐Aminobenzoic Acid Screening Test to Diagnose Pancreatic Insufficiency in Shwachman's Syndrome

Abstract

SummaryThe 6‐h urine recovery of p‐aminobenzoic acid (PABA) following the administration of a standard dose of N‐benzoyl‐L‐tyrosyl‐p‐aminobenzoic acid (BTPABA) was performed in 13 control subjects and two siblings with Shwachman“s syndrome. The control subjects showed a recovery of 67 ± 12.1% (mean ± 1 SD) of the administered dose, consistent with previously reported values. Unexpectedly, the recovery of PABA in two siblings with Shwachman's syndrome was found to be 67 and 63%, respectively. The values are well within the normal range. In these siblings, fecal chymotrypsin activities were very low when measured with N‐acetyl‐L‐tyrosyl‐ethyl ester (ATEE) as substrate, but were normal when BTPABA was the substrate. The duodenal juice of the younger affected child following pancreozymin‐secretin stimulation showed very low chymotrypsin activity against ATEE, BTPABA, and N‐benzoyl‐L ‐tyrosyl‐ethyl ester. These findings suggest that there may be BTPABA‐splitting activity in the lower bowel of these siblings with Shwachman's syndrome. This activity might be that of enteric bacteria or of the intestinal mucosa.