Background/Aims: Breath hydrogen testing is useful to assess colonic fermentation of malabsorbed carbohydrates and their role in symptom genesis. Specifically, lactulose and fructose breath responses can guide dietary restriction of FODMAPs (fermentable carbohydrates) in patients with irritable bowel syndrome (IBS). However, data regarding their reproducibility is limited. The aim was to investigate the reproducibility of lactulose and fructose breath tests.
Methods: A retrospective audit was conducted in 27 IBS patients completing a 15g lactulose breath test and in 32 patients ingesting 35g fructose. A repeat test was performed 6-8 weeks later for lactulose and ≥6 weeks for fructose. Changes in responses between test and retest were analysed qualitatively (positive response: 2 x ≥10ppm hydrogen rise) and quantitatively as area-under-curve (AUC)) and oro-caecal transit time (OCTT). The effect of duration between testing and variability was also assessed.
Results: A positive lactulose response was maintained in 96% subjects, but 31% (p=0.0006) lost a positive fructose response upon retest. Initial hydrogen AUC to lactulose and fructose were poorly correlated with hydrogen AUC values on repeat testing (lactulose: r2=0.08, p=0.16; fructose:r2=0.07, p=0.18; regression analysis). Such variations in fructose responses was independent of the duration between test and retest (r2=0.003, p=0.82. Lactulose OCTT (r=0.29; p=0.15; Spearman's correlation) or fructose (r=0.29; p=0.31) were not correlated between test-retest.
Conclusions: Poor reproducibility of lactulose and fructose breath testing was demonstrated. Making clinical decisions (e.g. malabsorptive diagnosis or to guide dietary fructose restriction) on the results of a single test cannot be justified.
Funding source(s): Fonterra™ & Yakult Australia.