CLINICAL APPLICABILITY OF SHORTENED D-XYLOSE BREATH TEST FOR DIAGNOSIS OF INTESTINAL MALABSORPTION

Urinary and/or plasmatic D-xylose tests are broadly used in clinical p ractice for the diagnosis of intestinal malabsorption. A 5-hr hydrogen breath test (H-2 BT) has also proven useful. Our goal was to determin e whether a shorter, hence more efficient, 3-hr test would perform as well as the 5-hr test. We studied 33 patients with proven malabsorptio n, 44 patients with irritable bowel syndrome (IBS), and 27 healthy sub jects. Each individual ingested 25 g of D-xylose, and alveolar breath samples were obtained thereafter at 30 min intervals for 5 hr. Breath samples were analyzed for H-2 by gas chromatography. Individual peak d elta changes and area under the curve (AUC) were calculated. Simultane ously, the 5-hr cumulative urinary excretion of D-xylose was measured by colorimetry. Results of 5-hr tests were compared with those of the first 3 hrs. In the malabsorption group, the 5-hr test showed a marked ly enhanced production of H-2 relative to healthy controls (delta: 60. 7 +/- 6.4 vs 7.7 +/- 1.5 and AUC: 8465.0 +/- 985.4 vs 393.2 +/- 232.6, P < 0.001 for both) and a reduced urinary excretion of D-xylose (2.8 +/- 0.3 g/5 hr vs 6.3 +/- 0.2, P < 0.001). Results in IBS patients did not differ from those in healthy controls. Three-hour analysis also r eflected an enhanced production of H-2 in the malabsorption group (del ta: 45.4 +/- 6.4 and AUC: 3700.0 +/- 545.6, P < 0.001 vs healthy contr ols). Correlation between 3-hr and 5-hr tests was significant in healt hy controls (r = 0.9), IBS (r = 0.9), and malabsorption (r = 0.8). The sensitivity of the 3-hr test was lower than of the 5-hr test (0.72 vs 0.91). The loss of sensitivity of the 3-hr test was attributed to a d elayed appearance of the delta peak in the malabsorption group. In con clusion, the H, breath test with D-xylose is a useful test for the dia gnosis of the intestinal malabsorption, but requires a 5-hr monitoring period to be reliable.