Comparison of the one-gram d-[14C]xylose breath test to the [14C]bile acid breath test in patients with small-intestine bacterial overgrowth

Dig Dis Sci. 1980 Jan;25(1):53-8. doi: 10.1007/BF01312733.


In twelve patients with culture-proven bacterial overgrowth of the small intestine, the ability of a newly-developed one-gram d-[14C]xylose breath test to detect bacterial overgrowth was compared to that of the [14C]bile acid breath test. All patients manifested excessive production of breath 14CO2 after the administration of one gram [14C]xylose, with 83% of the patients being abnormal within the first hour of testing. In contrast, during the [14C]bile acid breath test, four of the twelve patients had no period of excessive 14CO2 production (above the 95% confidence range of controls). Nutrient malabsorption (fat, cobalamin, xylose) was seen with both true-positive and false-negative bile acid breath tests. The one gram [14C]xylose breath test, utilizing a substrate with more predominant absorption in the proximal small intestine and which can be catabolized by Gram-negative aerobic bacteria, appears to have a greater degree of sensitivity and specificity than the bile acid breath test in detecting the presence of small-intestine bacterial overgrowth.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Bacterial Infections / diagnosis*
  • Bile Acids and Salts*
  • Blind Loop Syndrome / diagnosis
  • Breath Tests*
  • Carbon Dioxide / analysis
  • Carbon Radioisotopes
  • Humans
  • Intestinal Diseases / diagnosis*
  • Intestine, Small / microbiology
  • Xylose*


  • Bile Acids and Salts
  • Carbon Radioisotopes
  • Carbon Dioxide
  • Xylose