D-xylose hydrogen breath tests compared to absorption kinetics in human patients with and without malabsorption.

The D-xylose breath H2 test may be useful in characterizing intestinal absorptive function. Our aim was to determine whether breath H2 following D-xylose administration reflects the extent to which the D-xylose is absorbed by comparing it to a kinetic model of D-xylose absorption. Twenty-five subjects were studied. They ingested 15 g D-xylose on the first day and 25 g D-xylose on the third day. On the second day they received 10 g intravenous D-xylose along with 15 g oral lactulose. Multiple serum and urine samples were obtained for D-xylose content to calculate its rate constants and extent of absorption by multicompartmental analysis. Breath H2 determinations were obtained every 15 min for 3 hr following the 15 g D-xylose and lactulose ingestion. Peak breath H2 concentration correlated with extent of absorption (r = -0.787, P < 0.001), K0, the rate constant for nonabsorptive loss (r = 0.744, P < 0.001), and 5-hr urine content (r = -0.705, P < 0.001). Area under the breath H2 curve also correlated with these parameters: extent of absorption (r = -0.770, P < 0.001), K0 (r = 0.662, P < 0.001), 5-hr urine content (r = -0.629, P < 0.012). Peak D-xylose breath H2 to peak lactulose breath H2 showed no correlation with extent of absorption. The extent of absorption was higher with the 15-g dose than the 25-g dose in all patients tested (P < 0.01). (ABSTRACT TRANCATED AT 250 WORDS)