[Kinetics and clinical use of the combined D-xylose and NBT-PABA test]

The oral D-xylose- and NBT-PABA-test are frequently applied as screening methods for malassimilation syndromes. After oral load time-related serum concentrations are used as reference values. In this study both substances were given simultaneously as isotonic solutions after a fasting period of 6 hours. A standard meal was offered 20 minutes later. Blood samples were taken prior to and 60, 90 and 120 minutes after administration of the test-substances. 43 pediatric patients were studied. 11 patients with cystic fibrosis, 10 patients with underlying intestinal disease such as coeliac disease and cows milk intolerance and 22 patients with other than gastrointestinal diseases were compared. In children with coeliac disease and cows milk intolerance 1-hour PABA concentrations were in the range of the control group whereas 1-hour D-xylose concentrations were lower than 15 mg/dl. In patients with cystic fibrosis the maximum concentrations of D-xylose were within the limits of normal values while 1-hour PABA concentrations were lower than 0.15 mg/dl in cases of relevant exocrine pancreatic insufficiency. The results of this study show that the combined D-xylose and NBT-PABA-test has proved its practical value in cases of suspected malassimilation and its discriminatory property between patients with relevant pancreatic insufficiency and patients with diminished intestinal absorptive capacity due to coeliac disease or cow's milk intolerance.