Send to

Choose Destination
J Clin Gastroenterol. 2001 Jul;33(1):36-40.

Improving the serum D-xylose test for the identification of patients with small intestinal malabsorption.

Author information

Division of Gastroenterology, Department of Medicine, University of Chicago Hospitals, 5841 South Maryland Avenue, Chicago, IL 60637, U.S.A.



D-Xylose absorption testing is a simple, low-cost method of screening for small intestinal malabsorption. The optimum method to measure D-xylose absorption (serum vs. urine testing) is uncertain.


We present a method of improving the accuracy of D-xylose testing.


Fifty-one consecutive patients (40 with chronic diarrhea and 5 asymptomatic patients with renal insufficiency) and 6 volunteers with normal renal function were recruited. All received D-xylose, 10 g intravenously and 25 mg orally, on two separate occasions. Serum concentration was determined at baseline and at frequent times thereafter. Area under the curve was calculated to infinity, and D-xylose bioavailability (F) was calculated. A nonlinear model used to derive the relationship between 3-hour D-xylose concentrations and F showed that a value of less than 22.5 mg/dL correlated with an F of less than 60% (malabsorption of D-xylose). A 1-hour D-xylose of less than 20 mg/dL was considered abnormal.


Using these indexes for normal 1-and 3-hour D-xylose levels, 90% of patients with D-xylose malabsorption were identified (sensitivity, 90%; specificity, 95%), which represents a marked improvement within the conventional 1-hour D-xylose of less than 20 mg/dL alone (sensitivity, 71%; specificity, 100%). The model was applied prospectively to 15 additional patients with chronic diarrhea. Of these, 12 patients with an F of less than 60% were identified, including 2 patients with normal 1-hour D-xylose levels.


Thus, the addition of a 3-hour D-xylose serum level of less than 22.5 mg/dL to conventional 1-hour D-xylose determination greatly improves the D-xylose test for malabsorption screening.

[Indexed for MEDLINE]

Supplemental Content

Full text links

Icon for Wolters Kluwer
Loading ...
Support Center