One-hour blood xylose test: a reliable index of small bowel function.

A retrospective analysis of oral D-xylose tolerance tests in 435 pediatric patients was performed. A significant difference was found between 126 normal subjects and 47 untreated children with celiac disease one hour after load. The one-hour value was found to be more reliable than was fecal fat analysis in screening children for celiac disease. Sex, age, weight, and body surface did not influence the results of the one-hour value in the control subjects. Forty-eight children with cystic fibrosis had one-hour xylose levels within the normal range, but the means at 90, 120, and 180 minutes after load exceeded significantly (P less than 0.01) those of the controls. In a nonceliac group of 63 children with abnormally low xylose levels, almost all were found to have clinical conditions compatible with upper small bowel mucosal impairment. This study shows that a single estimation of xylose in blood one hour after load is a reliable index of small bowel mucosal function. It is a good screening test for celiac disease and small bowel disorders producing malabsorption in children.