Comparison of the 1-gram C-14-D-xylose breath test and the 50-gram hydrogen glucose breath test for diagnosis of small intestinal bacterial overgrowth

Background/Aims: Culture of small bower aspirate is the most direct method and the gold standard for diagnosing small intestinal bacterial overgrowth. However, cultures are cumbersome and fluoroscopy is required for obtaining aspirate. Therefore, different breath tests such as the xylose breath test and the hydrogen breath test have been developed. There is no general agre ement as to which test is to be preferred. In the only previous direct comp arison between these two tests an advantage for the 1-gram-C-14-D-xylose br eath test was found. The aim of the study was to compare the 50-gram glucos e hydrogen breath test and the 1-gram C-14-D-xylose breath test in relation to results of cultures of small bowel aspirate. Methods: Forty-six consecu tive patients, mean age 57 (range 27-87) years, 12 men and 34 women, were i ncluded because of suspicion of small intestinal bacterial overgrowth. Afte r small bowel aspiration, all patients received a solution of 1 g xylose, l abelled with 50 mu g C-14- D-xylose, and 50 g glucose dissolved in 250 mi w ater. The concentration of breath hydrogen was analyzed every 15 min for 2 h and (CO2)-C-14 was analyzed every 30 min for 4 h. A positive hydrogen bre ath test was defined as a rise in hydrogen concentration of 15 ppm. A posit ive xylose test was defined as an accumulated dose 4.5% after 4 h. Two defi nitions for a positive culture were used, either growth of 10(5) colonic-ty pe bacteria/ml or growth of 10(5) bacteria/ml of any type. Results: Twenty- four patients had growth of 10(5) bacteria, of whom 10 had growth of 10(5) colonic-type bacteria in small bowel aspirate. Twenty-two patients had no s ignificant growth. The hydrogen breath test and the xylose breath test had a sensitivity for growth of 10(5) bacteria of 58 and 42%, respectively. For growth of 10(5) colonic-type bacteria the sensitivity was 90% for the hydr ogen breath test and 70% for the xylose breath test. The specificity was si milar for the two tests. Conclusion: Although no significant difference bet ween the two tests was found, there was a tendency in favor of the 50-gram glucose hydrogen breath test. The simplicity in combination with high sensi tivity makes the hydrogen breath test suitable as a screening method to sel ect patients for further investigation. Copyright (C) 2000 S. Karger AG. Ba sel.