The acquisition parameters and interpretation of breath testing data for the assessment of carbohydrate malabsorption (CM) varies widely between centres. The North American Consensus (NAC) document on breath testing published in 2017 was a first attempt to standardise this diagnostic test. Two key recommendations were to extend the period of post ingestion breath sampling from 120 to 180 min and that SIBO should be excluded prior to CM testing. We retrospectively assessed our database of CM studies from the previous 12 months to examine the impact of these recommendations on results.Methods
Patient data was retrospectively attributed to 120 min and 180 min groups for both lactose and fructose breath tests. All patients provided a baseline sample prior to ingestion of 25 g of either substrate following a 24 hour restrictive diet and 12 hour fast. In total 200 breath tests were analysed (120-lactose and 80-fructose). A rise >20 ppm above baseline was considered positive for CM. The results were compared statistically using Pearson’s chi-squared test.Results
A positive result for CM at 120 min was seen in 27 of 120 (22.5%) subjects for lactose and 33 of 80 (36.3%) subjects for fructose. When extended to 180 min the number of positive CM tests increased to 30% and 41.3% for lactose and fructose, respectively. Within these sub-groups the significant rise in gas levels occurred at ≤60 min after ingestion in 34.3% for lactose and 69.8% for fructose. There was a significant association between patients who had a positive SIBO test (as determined by a separate lactulose test) and a positive breath test for lactose at ≤60 min [χ2≥5.3, p0.02]. Findings for fructose were not significant [p>0.05].Conclusions
Around 20% of the positive results for CM occurred after 120 min supporting the NAC position to extend the post ingestion period to 180 min to avoid false negative studies. SIBO may influence results and a lactulose breath test should be performed prior to CM testing to avoid false positive tests and to help interpret CM studies with greater accuracy. Like the first iteration of the Chicago Classification for oesophageal motility testing – the NAC on breath testing represents a positive first step in standardising these diagnostic tests.