BT-Paba test in the diagnosis of pancreatic exocrine insufficiency in cystic fibrosis: urinary and serum determinations compared.

Urinary recovery and serum determination of Paba were carried out in 48 control children (C) and 53 paediatric patients with cystic fibrosis (CF) divided into three classes by age. Ninety and 120 min after the ingestion of 15 mg/kg of BT-Paba and of a standard meal, serum Paba was determined. In the same subjects the percentage Paba recovery was measured in the urine collected during an 8 h period after the same administration of BT-Paba. Correlation between urinary and serum Paba values was higher in the older children in respect to the 0-2-year-old infants. A urinary Paba test was less sensitive and specific than a serum Paba test in the evaluation of exocrine pancreatic function. The best discrimination between C and children with CF, using the maximal value of serum Paba at 90 or 120 min (peak), was obtained in the younger infants (0-2 years old). BT-Paba test with serum Paba peak determination is recommended as a substitute for the classical urinary Paba test in the evaluation of exocrine pancreatic function in paediatric patients, especially in the younger infants.