Intestinal malabsorption of D-xylose: Comparison of test modalities in patients with celiac disease

Objective. The aim of the study was to compare three different D-xylose test modalities for small intestinal malabsorption, using patients with celiac disease and healthy persons as experimental models. Material and methods. Ninety-one untreated celiac patients, 98 treated celiac patients, and 43 healthy subjects performed the C-13-D-xylose breath test. 1-h plasma D-xylose levels were measured in 48 untreated patients, 41 treated patients and 41 healthy controls. 4-h urine D-xylose excretion was measured in 47 untreated patients, 51 treated patients and 42 healthy controls. 100 mg of C-13-D-xylose and 5 g of D-xylose were dissolved in 250 ml tap water and given orally. (CO2)-C-13 was measured in breath every 30 min for 4 h. Blood was sampled after 1 h, and urine collected after 4 h. Results. Test sensitivity/specificity for celiac disease was 88%/84% with the C-13-D-xylose breath test, 65%/71% with the 1-h plasma D-xylose test, and 55%/74% with the 4-h urine D-xylose excretion test. Breath test results improved significantly in the treated celiac group compared to untreated patients, but were not normalized compared to healthy controls. No difference was found between 1-h plasma D-xylose levels and 4-h urinary D-xylose excretion in treated celiac patients and healthy controls. Conclusions. The C-13-D-xylose breath test was superior to D-xylose testing in plasma and urine for assessment of small intestinal malabsorption with considerably higher sensitivity and specificity for untreated celiac disease.