xylose breath test

Last reviewed 01/2018

The 14C-xylose breath test a highly specific and sensitive test of bacterial overgrowth in the small intestine. It depends on the ability of anaerobic bacteria to metabolise 14C-xylose with the production of 14CO2, that is absorbed from the intestine and excreted in the expired air.

Following an overnight fast, 1 g of unlabelled D-xylose is taken orally together with 2 mGy of 14C-xylose in 250 ml of water. The amount of 14CO2 in the expired air is measured.

The test is positive if the amount of 14CO2 collected within 30 minutes exceeds 0.00013% of the administered dose. In patients with delayed gastric emptying, a longer period of collection may be necessary.