IMPROVEMENT IN SPECIFICITY OF [C-14] D-XYLOSE BREATH TEST FOR BACTERIAL OVERGROWTH

The aim of the study was to determine whether the specificity of the [ C-14]d-xylose breath test could be improved, by excluding false-positi ve tests due to premature colonic metabolism of the [C-14]d-xylose cau sed by rapid colonic transit. Forty-seven patients with suspected smal l bowel bacterial overgrowth were investigated by (1) aspiration and c ulture of duodenal fluid and (2) a [C-14]d-xylose breath test. Those w ith either a positive duodenal culture or breath test had a repeat [C- 14]d-xylose breath test given with one of three transit markers (bariu m, Gastrografin or Tc-99m-labeled tin colloid) to determine if the sit e of metabolism was in the small bowel or colon. Fourteen patients had positive duodenal cultures, four of whom had a negative [C-14]d-xylos e breath test, 15 patients had a positive [C-14]d-xylose breath test, three of which were due to colonic metabolism of the xylose. Where tra nsit markers were used, C-14 was detectable in the breath and serum be fore barium had entered the small bowel, thus the barium did not comig rate with the xylose. Gastrografin accelerated small bowel transit, le ading to malabsorption of the xylose in the small intestine and subseq uent colonic metabolism of the xylose. Tc-99m-labeled tin colloid had no obvious disadvantages and appeared to be the marker of choice. The use of a transit marker increased the specificity of the [C-14]d-xylos e breath test from 85% to 94%. The specificity of the [C-14]d-xylose b reath test for the detection of small bowel bacterial overgrowth is im proved to greater than 90% by the use of an appropriate transit marker .