Hydrogen (H2) and Methane (CH4) breath testing
The number of Breath Tests (BTs) being ordered by health care professionals is rising (including the use of mail order breath tests), but the lack of standardisation regarding the indications, preparation and performance and interpretation of BT has led to considerable diversity between different centres and practitioners partly due to the genetic heterogeneity of human populations.
Typical BT Conditions
Fructose malabsorption - the patient takes a base reading of hydrogen levels in his/her breath. The patient is then given a small amount of fructose, and then required to take readings every 15, 30 or 60 minutes for two to three hours. If the level of hydrogen rises above 20 ppm (parts per million) over the lowest preceding value within the test period, the patient is typically diagnosed as a fructose malabsorber. If the patient produces methane then the parts per million for the methane typically rises 12 ppm over the lowest preceding value to be considered positive. If the patient produces both hydrogen and methane then the values are typically added together and the mean of the numbers is used to determine positive results, usually 15 ppm over the lowest preceding value.
Lactose malabsorption - the patient takes a base reading of hydrogen levels in his/her breath. The patient is then given a small amount of pure lactose (typically 20 to 25 g), and then required to take readings every 15, 30 or 60 minutes for two to three hours. If the level of hydrogen rises above 20 ppm (parts per million) over the lowest preceding value within the test period, the patient is typically diagnosed as a lactose malabsorber. If the patient produces methane then the parts per million for the methane typically rises 12 ppm over the lowest preceding value to be considered positive. If the patient produces both hydrogen and methane then the values are typically added together and the mean of the numbers is used to determine positive results, usually 15 ppm over the lowest preceding value. However, recent studies suggest that testing may not correlate with any actual diagnosis.
Small Bowel Bacterial Overgrowth Syndrome (SBBOS) or Small Intestinal Bacterial overgrowth (SIBO) – the patient is either given a challenge dose of glucose, also known as dextrose (75-100 grams), or lactulose (10 grams). Breath samples are then collected at 15 minute or 20 minute intervals after the baseline is collected for 3-5 hours.
Positive diagnosis for a lactulose SIBO breath test - typically positive if the patient produces approximately 20 ppm of hydrogen and/or methane within the first two hours (indicates bacteria in the small intestine), followed by a much larger peak (colonic response).
This is also known as a biphasic pattern. Lactulose is not absorbed by the digestive system and can help determine distal end bacterial overgrowth, which means the bacteria are lower in the small intestine. Positive diagnosis for a glucose SIBO breath test - glucose is absorbed by the digestive system so studies have shown it to be harder to diagnose distal end bacterial overgrowth since the glucose typically doesn't reach the colon before being absorbed.
An increase of approximately 12 ppm or more in hydrogen and/or methane during the breath test could conclude bacterial overgrowth. The excess hydrogen or methane is assumed to be typically caused by an overgrowth of otherwise normal intestinal bacteria.
Reliability of end-expiratory hydrogen (H2) breath tests have been assessed using a compact, rapid H2-monitors with electrochemical cells. The H2 response was shown to be linear and stable. It is concluded that the technique used for interval sampling of end-expiratory breath samples for H2 concentration gives reliable results. The biological significance of H2 concentration increments can only be evaluated if the limitations of the technical procedures and the individual ability to produce H2 is known.
Breath testing (BT) is performed to aid in the diagnosis of many common gastroenterological conditions including small intestinal bacterial overgrowth (SIBO) and irritable bowel syndrome (IBS)-like symptoms, carbohydrate maldigestion and dysfunction or alterations in oro-cecal transit. Presently in clinical practice, BT is being performed with various substrates (e.g., glucose, lactulose, fructose, sorbitol, sucrose and inulin), as shown in the sugar test image below, using variable doses for a range of established and unestablished indications (e.g., SIBO, orocecal-transit time assessment and carbohydrate maldigestion).
New technology can assist in detecting gastrointestinal disorders. Breath analysis monitoring can measure accurate and real-time combined CH4, H2 and O2. CH4 is produced in the human intestine mostly by an H2-utilizing flora. Therefore, adequate assessment of gut bacterial carbohydrate fermentation would require parallel, accurate and real-time combined CH4, H2 and O2 testing.
A portable breath CH4, H2 and O2 monitor can help health professionals to detect a range of gastrointestinal disorders. A percentage of patients do not produce hydrogen and therefore would not be diagnosed by the use of hydrogen breath testing (HBT) alone. Therefore the role of methane is to ensure that patients who are non-hydrogen producers, but produce methane instead, are not misdiagnosed.
Breath testing can be used to help detect the following disorders:
- Lactose intolerance
- Fructose intolerance
- Glucose intolerance
- Irritable Bowel Syndrome (IBS)
- Small Intestinal Bacterial Overgrowth (SIBO)
There are many portable hand-held breath hydrogen monitors available that have been developed to aid in the detection of gastro-intestinal disorders such as carbohydrate intolerances and malabsorption, intestinal bacterial overgrowth and for determining intestinal transit time.
Hydrogen is generated in the intestinal lumen by bacterial action on carbohydrates in the large or small intestine. This resultant hydrogen diffuses into the blood stream and thereafter to the alveoli after which it can be detected in expiratory air.
A hydrogen breath test (or HBT) is used as a clinical medical diagnosis for people with irritable bowel syndrome, and common food intolerances. The test is simple, non-invasive, and is performed after a short period of fasting (typically 8-12 hours). Even though the test is normally known as a "Hydrogen Breath Test" some physicians may also test for methane in addition to hydrogen. Many studies have shown that some patients (approximately 35% or more) do not produce hydrogen but actually produce methane. Some patients produce a combination of the two gases. Other patients don't produce any gas, which are known as "Non-Responders"; some physicians believe that these individuals actually produce another gas which has not been determined yet.
In addition to hydrogen and methane, some facilities also utilize carbon dioxide (CO2) in the patients' breath to determine if the breath samples that are being analyzed are not contaminated (either with room air or bronchial dead space air).
Breath testing remains a useful, inexpensive, simple, and safe diagnostic tool in gastroenterology. Using an evidence-based approach, consensus was reached on 26 statements providing practical guidance regarding the indications, preparation, performance and interpretation of BT in clinical practice and research. Furthermore, current gaps of knowledge are identified for future research directives. As compared to previous guidelines, these consensus statements are updated based on the most recent literature and provide detailed recommendations and clarity on drug regimens prior to BT, dose of substrates, established indications, limitations and interpretation of the results based on both hydrogen and methane gases.
Edited by John Sandham.