Hydrogen and methane breath tests (HMBT) are a noninvasive diagnostic tool commonly employed to evaluate small intestinal bacterial overgrowth (SIBO) and issues with carbohydrate malabsorption, such as lactose and fructose intolerance. While this technique is frequently used in adults, its application in children is not as standardized, leading to uncertainties regarding the adoption of adult protocols for the pediatric population.
The following article discusses the use of HMBT in children, presents the key considerations for interpreting results, and examines the most reliable available guidelines, particularly the 2017 North American Consensus.
Background and current challenges to HMBT
SIBO and carbohydrate malabsorption, such as lactose and fructose intolerance, can lead to gastrointestinal symptoms in children and adults, such as bloating, diarrhea, abdominal pain, and malnutrition. In pediatric clinics, nutritional deficiencies that fail to thrive present a significant challenge. Since children need a steady intake of nutrients for proper growth, precise diagnosis is particularly important in this demographic.
Although the demand for HMBTs in children is critical, there is a notable lack of literature focused on this age group, forcing testing clinics to depend on the more established consensus guidelines for adults. Adapting adult HMBT protocols for children presents major challenges due to variations in gut physiology, metabolic rates, and transit times.
The European Society for Paediatric Gastroenterology, Hepatology, and Nutrition (ESPGHAN) has released guidelines for pediatric breath testing; however, these guidelines have limitations, such as inconsistencies in test execution, absence of pediatric-specific threshold values, and variability in the interpretation of results. This has resulted in a reluctance to adopt these guidelines in clinical practice fully.
Consequently, many experts suggest adhering to the 2017 North American Consensus guidelines, even though they were primarily created for adults. The North American Consensus provides more comprehensive guidance that can be tailored for pediatric applications with careful attention.
Testing protocols and dosages for children
Despite the lack of pediatric-specific guidelines, a dependable approach is to use the same substrates and dosages recommended for adults. For instance, the North American Consensus suggests using:
- Lactulose: 10 g or 15 mL for diagnosing SIBO
- Lactose or fructose: 25 g for diagnosing intolerance
It is crucial to recognize that while these dosages are suitable for adults, they may be excessive for children. For instance, a 25 g dose of lactose is approximately the same as drinking 500 mL of milk, which could be too much for a child and may result in false positives. As a result, clinicians need to be careful when interpreting positive results and should always consider the child's capacity to absorb these amounts.
Just like in adults, it is essential to prioritize ruling out SIBO before assessing for intolerance in children. SIBO can lead to secondary malabsorption and intolerance, meaning that addressing SIBO could alleviate symptoms of carbohydrate intolerance.
This is especially critical for pediatric patients, as diagnosing lactose intolerance can significantly limit the vital nutrients necessary for healthy childhood development.
SIBO testing and the role of methane
Lactulose is generally used as the substrate to test for SIBO. Lactulose is fermented by the bacteria in the small intestine and is a non-absorbable sugar, producing hydrogen (H2) and methane (CH4) because of the fermentation. The consensus suggests using a 20 ppm rise in H2 from the baseline as the threshold for diagnosing SIBO.
Although this threshold was designed for adults, it can also serve as a cautious guideline for pediatric populations. It is considered conservative because if the test returns negative for SIBO after administering an adult dose of lactulose, SIBO can be excluded. In children, a positive result for SIBO might stem from rapid oro-caecal transit due to a shorter gastrointestinal tract or faster gut motility.
Thus, a positive result is not definitive unless a pediatric oro-caecal transit study verifies the timing of lactulose transit for that specific patient to aid in interpretation.
Methane detection in children: Thresholds, prevalence, and clinical implications
Detecting CH4 is crucial in hydrogen and methane breath testing (HMBT) for identifying intestinal methanogen overgrowth (IMO). Elevated CH4 production is associated with slower gastrointestinal motility, which contributes to constipation, a common issue in children with IMO.
High CH4 levels indicate the presence of methanogenic flora and underscore the need for targeted treatments to alleviate gastrointestinal symptoms like bloating and malabsorption, especially in children whose growth and nutrient absorption are vital.
One key factor in interpreting breath test results in children is oro-caecal transit time, which does not seem to affect CH4 analysis. Unlike H2 production, which can vary with rapid transit, CH4 detection remains unaffected by how quickly food moves through the small intestine.
This makes CH4 results more reliable in adult and pediatric populations, reducing the likelihood of false positives or negatives related to gut transit time. When considering CH4 thresholds, it is important to recognize the differences in methanogen prevalence between children and adults.
Research, including one by Vanderhaeghen et al. (2015), demonstrated that children typically possess a lower prevalence of methanogens such as Methanobrevibacter smithii. The study's findings indicated that 65% of children had detectable levels of methanogens compared to 89% of adults, and the relative abundance of methanogens in children was lower (0.15% vs. 0.52%).
Despite this lower prevalence, it does not mean that CH4 production is consistently low among children with detectable methanogens. Those children may still produce CH4 levels similar to adults since the metabolic activity of Methanobrevibacter smithii is influenced more by substrate availability than by species prevalence. Although fewer children may test positive for CH4, those who do might produce significant amounts.
The same study highlighted that children who host methanogenic species tend to produce less CH4, suggesting that using adult thresholds could lead to underdiagnosis. Therefore, applying the 10 ppm threshold for CH4 in children is considered a conservative approach, preventing overdiagnosis of methanogen overgrowth.
Given these findings, maintaining the adult threshold of 10 ppm for CH4 in children seems wise, as it minimizes false positives. A positive result can be confidently viewed as evidence of CH4 overproduction, potentially linked to conditions like IMO.
However, negative results may still create uncertainty, as the lower prevalence of methanogens in children means that the absence of detectable CH4 does not completely rule out overgrowth in those with small but metabolically active populations.
Testing for lactose and fructose intolerance
Once SIBO or IMO has been ruled out, lactose and fructose intolerance testing can be conducted. The same dosages used in adult testing—25 g of lactose or fructose—may be used in children. Due to shorter oro-caecal transit times in children, there is a heightened risk of false-positive results.
Clinicians should consider that a 25 g dose may exceed a child’s typical absorption capacity, leading to test results that do not accurately reflect their usual dietary intake. This could also lead to false-positive test results that do not necessarily reflect the child’s usual dietary intake, which may only involve smaller quantities of these sugars.
Generally, a negative result is more reliable, even with the high adult doses of substrates and the potential for rapid transit or reduced absorption in children.
Oro-caecal transit time and confirmation of results
A challenge in interpreting breath test results, particularly in children, is determining whether an increase in H2 or CH4 genuinely indicates SIBO or merely reflects normal oro-caecal transit.
Scintigraphy can confirm oro-caecal transit time, allowing clinicians to ensure that the timing to reach the caecum aligns with the breath test's expectations. This step is vital for preventing false positives and enhancing diagnostic accuracy.
Limitations of alternative tests for lactose intolerance
Genetic testing (LCT gene) and intestinal biopsies are alternative methods some clinicians consider for diagnosing lactose intolerance. While genetic tests can help identify congenital lactase deficiency (CLD), they have limitations. Acquired lactose intolerance, the most common type, is not uniformly detectable through genetic testing, as lactase production can vary along the intestinal lining. Similarly, biopsies may yield false-negative or false-positive results depending on the sampling site. LCT testing does not aid in monitoring treatment responses or dietary changes, and not all individuals with a positive LCT test are genuinely lactose intolerant.
Another diagnostic method is the lactose tolerance test (LTT), which measures blood glucose levels after lactose ingestion. If lactose is properly digested, blood glucose should rise. However, this test is not standardized for children and varies considerably in execution and interpretation, making it less reliable than breath testing in pediatric populations.
HMBT offers distinct advantages over these methods. It provides a non-invasive way to directly measure H2 and CH4 gases produced by undigested lactose fermentation in the colon. This method effectively detects lactose malabsorption, whether congenital or acquired, and allows for monitoring treatment or dietary response, offering a comprehensive approach to managing lactose intolerance.
Conclusion and future directions
HMBT is one of the most reliable diagnostic tools for assessing SIBO and carbohydrate malabsorption. While no definitive pediatric protocol exists, the North American Consensus guidelines are a solid foundation for adapting adult protocols for younger patients.
Clinicians should exercise caution when interpreting positive results, especially when substrate doses may be excessive for children or when quicker oro-caecal transit could lead to false positives. Ruling out SIBO or IMO should always be the initial step, as addressing these underlying conditions often alleviates intolerance symptoms.
Ultimately, HMBT remains the most practical method for diagnosing SIBO and carbohydrate malabsorption in pediatric patients. However, further research is essential to refine protocols, establish pediatric-specific thresholds, and enhance testing accuracy and interpretation for this vulnerable population.
HMBT with the Gastrolyzer® range
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References
- Rezaie, A., et al. (2017). Hydrogen and Methane-Based Breath Testing in Gastrointestinal Disorders: The North American Consensus. The American Journal of Gastroenterology, (online) 112(5), pp.775–784. https://doi.org/10.1038/ajg.2017.46.
- Di Lorenzo, C., et al. (2019). "Gastrointestinal Motility in Children." Journal of Pediatric Gastroenterology and Nutrition, 68(6), 759-770.
- Furnari, M., et al. (2018). "Breath Tests for Small Intestinal Bacterial Overgrowth: A Comprehensive Review." Gut and Liver, 12(4), 403-412.
- He, T., et al. (2017). "Lactose Intolerance and Genetic Testing: An Overview." European Journal of Pediatrics, 176(8), 1113-1121.
- Szajewska, H., et al. (2018). "Lactose Intolerance in Children: A Position Paper by the European Society for Paediatric Gastroenterology, Hepatology and Nutrition (ESPGHAN)." Journal of Pediatric Gastroenterology and Nutrition, 66(1), 165-174.
- Vanderhaeghen, S., Lacroix, C. and Schwab, C. (2015). Methanogen communities in stools of humans of different age and health status and co-occurrence with bacteria. 362(13), pp.fnv092–fnv092. https://doi.org/10.1093/femsle/fnv092.
- Ghali, M. B., et al. (2017). "Gut methanogens: Methanobrevibacter smithii and health in children and adults." Journals of Microbiology.
- Shreiner, A.B., Kao, J.Y. and Young, V.B. (2015). The gut microbiome in health and in disease. Current Opinion in Gastroenterology, 31(1), pp.69–75. https://doi.org/10.1097/mog.0000000000000139.
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