¹³C-xylose and ¹⁴C-xylose breath tests for the diagnosis of coeliac disease

Abstract

Objectives. Xylose absorption testing has traditionally involved measurement of serum xylose and/or measurement of excreted xylose in urine. However, by enriching xylose with a ¹³C- or ¹⁴C-isotope, absorption of an oral xylose load will be reflected in the time-dependent pattern of ¹³CO₂ or ¹⁴CO₂ exhaled in breath. Our objectives were to evaluate the diagnostic properties of ¹³C-xylose and ¹⁴C-xylose breath tests in coeliac disease, and to develop a diagnostic breath test index. Material andmethods. We reviewed data from 41 coeliac patients who underwent the ¹⁴C-xylose breath test before and after commencement of a gluten-free diet, and 60 coeliac patients who underwent the ¹³C-xylose breath test, 37 of whom repeated the test after starting a gluten-free diet. Coeliac patients were compared with healthy control subjects. Results. Coeliac patients exhaled significantly less ¹³CO₂ or ¹⁴CO₂ than healthy controls during the first hour of the test and more isotope-labelled CO₂ than control subjects after 3 h. Diagnostic accuracy was optimal with test duration of 210 min combining gas measurements at 30 min and 210 min in a simple fraction. This gas fraction index (30 min/210 min) distinguished between coeliac patients and healthy control subjects with 84–95% sensitivity and 87–94% specificity. After commencement of a gluten-free diet, the gas fraction index increased in most coeliac patients, but remained lower than that in healthy control subjects. Conclusions.¹³C-xylose- and ¹⁴C-xylose breath tests discriminate between coeliac patients and healthy control subjects with high sensitivity and specificity. The stable isotope ¹³C-xylose breath test has comparable diagnostic accuracy to the radioactive isotope ¹⁴C-xylose breath test and should be the preferred alternative to traditional xylose absorption tests.

• Breath test
• carbon isotopes
• coeliac disease
• malabsorption
• xylose