Xylose-1-14C absorption test: the use of urine, serum and breath analysis, and comparison with a colorimetric assay.

The xylose absorption and excretion test has been reassessed in controls and patients with coeliac disease. Xylose has been assayed in both serum and urine colorimetrically and by liquid scintillation counting using xylose-1-14C. The excretion of 14CO2 in breath following administration of xylose-1-14C has been measured. Liquid scintillation counting is a simple and reliable method for the measurement of xylose absorption. Serum xylose levels, urinary xylose excretion, or breath 14CO2 in isolation were poor screening tests for mucosal disease. The use of serum levels and urinary excretion in combination improved the discriminatory value of the test though small gut biopsy was more reliable.