Blood xylose as a screening test for malabsorption in jejunal mucosa abnormalities; importance of diet in interpretation

Blood xylose level 60 min. after an oral dose of 10 g/m2 xylose was compared with the histology of the jejunal mucosa in 56 children. Ninety-two percent of children with blood xylose below 20 mg/100 ml had an abnormal jejunal mucosa; 98% of children with a normal mucosa had a blood xylose above 20 mg/100 ml. In children with coeliac disease the following observations were made: 1) blood xylose was above 20 mg/100 ml in 50% of children with flat mucosa; all were given a diet excluding gluten; 2) blood xylose levels which were initially below 20 mg/100 ml were found above this level 3 to 12 days after the onset of the diet; 3) all the histological relapses following re-introduction of gluten in the diet were not associated with a decrease of blood xylose level below 20 mg/100 ml.