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Hydrogen Breath Testing
Hydrogen ( H2 ) breath testing is used to investigate patients with irritable bowel syndrome (IBS), food intolerances and suspected bacterial overgrowth syndromes. Breath hydrogen tests provide clinicians with a scientific basis to plan low FODMAP diets for their patients and to advise on dietary exclusions. The tests are now used routinely in gastroenterology, are simple, non-invasive and are performed after a short period of fasting. This clinician’s guide addresses the principles behind the tests, how they are conducted, appropriate patient selection and result interpretation.
Why test for breath Hydrogen ?
In humans, hydrogen gas is produced by bacterial fermentation of carbohydrates that are incompletely absorbed in the small intestine and delivered undigested to the large intestine. Hydrogen, methane, short chain fatty acids, acetate and sulfides are the byproducts of this process and may be responsible for intestinal bloating, abdominal pain, wind, diarrhoea and other reported symptoms of the irritable bowel syndrome (IBS). Intestinal gas is passed as flatus but also absorbed across the intestinal mucosa into the blood stream. Gas transfer at the lungs allows measurement of expired breath hydrogen.
Recently described FODMAPs (Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols) including lactose ,fructose and sorbitol are poorly absorbed in patients with IBS and are strongly implicated in the pathogenesis of symptoms. FODMAPs are not only subject to fermentation and excess gas production but are also highly osmotic drawing fluid into the bowel further altering gut motility.
Small bowel bacterial overgrowth (SIBO) should all be considered in the aetiology of functional gut syndromes.
Breath testing for hydrogen production provides a reliable method of identifying patients with functional gut syndromes associated with carbohydrate malabsorption and those with small intestinal bacterial overgrowth.
It is important to note that breath hydrogen is derived wholly from bacterial fermentation, there is no other physiological source of hydrogen in the human body. A small group of test patients ( about 10% ) may be predominant methane producers. Very little hydrogen is found in the breath of these patients despite active gastrointestinal symptoms. Lactulose testing conducted as part of the recommended panel of tests identifies this cohort.
What tests are available?
Lactulose: Lactulose is not absorbed across the small intestinal mucosa and is used to assess hydrogen production. Lactulose testing also measures small bowel transit time and is utilized to assess bacterial fermentation in the small bowel (bacterial overgrowth) where an early peak in hydrogen production is observed. An absence of H2 production with lactulose indicates predominant methane production, symptom recording in this cohort helps to identify intolerance.
Lactose: This is used to measure how well the lactase enzyme system is working and investigates lactose intolerance.
Fructose: This is the sugar commonly found in fruits, fruit juices and confectionary. Complex fructose molecules are referred to as fructans and these can be found in onions, lentils and other vegetables.
Sorbitol: This is present in common fruits such as apples and pears as well as artificial sweeteners.
Glucose: Can be used as an aid in testing for small intestinal bacterial overgrowth
Who should be tested ?
Testing should be considered in patients with IBS, specific food intolerances and in those suspected of having small intestinal bacterial overgrowth ( SIBO ).
Bloating, generalised abdominal discomfort, passage of excessive flatus and altered bowel habit identifies patients who may benefit from further analysis.
Current data suggests that 45% of the Australian population have fructose intolerance. Lactose intolerance is present in 10-15% of Caucasians and in up to 85% of Asians. Consumption of fructose or lactose in these patients may result in IBS like symptoms.
Patients with IBS commonly have intolerance to FODMAP’s including complex fructose molecules called fructans.
Studies show that up to 75% of patients with IBS experience a significant improvement in symptoms with dietary manipulation.
Small intestinal bacterial overgrowth syndromes ( SIBO ) occurs where there is altered gut transit as seen in some patients with scleroderma and where surgical blind loops exist. SIBO may also be seen in patients with more typical IBS like symptoms even in the absence of scleroderma or previous surgical history.
Indications for Testing
Suspected lactose intolerance
Suspected fructose intolerance
Suspected small intestinal bacterial overgrowth
How is the test performed ?
A safe and simple hand held gas analyser machine (gastrolyser) is used to detect small amounts of exhaled hydrogen after patients ingest a test dose of carbohydrate. An exclusion diet is followed the evening before the test and a 5 hour fast required. A baseline hydrogen value is taken before test carbohydrates are administered.
A standard dose of a specific carbohydrate (fructose, lactose or sorbitol, etc.) is ingested and readings are taken at 20 minute intervals looking for a rise of at least 20 ppm of H2. If there is no increase in breath hydrogen and no abnormal symptoms the test carbohydrate has been completely absorbed. A rise in breath H2 of more than 20ppm indicates incomplete absorption of the test sugar and intolerance.
During the analysis symptoms are recorded and must be considered along with the measured hydrogen levels to establish the diagnosis of carbohydrate intolerance.
Only one test can be performed per day, a 2-3 day break is required between testing.
Testing is noninvasive, takes 2-3 hours, and is safe for all ages over 5 years . Testing may be performed during pregnancy after exclusion of gestational diabetes. Diabetic patients must contact the testing centre before investigation to discuss glycaemic control.
The results are entered into a central computer which has sophisticated algorithms and graphs specific for each test, the results are then reviewed and validated by scientific staff and a Gastroenterologist before being forwarded to the patient or transmitted to the General Practitioner via Argus.
Where can I have my Breath test performed ?
Testing for lactulose fructose, lactose, sorbitol, and glucose can be performed by Melbourne Breath Test in one of its collection centers that has been equipped for hydrogen breath testing.
Many of our centres offer testing on a daily basis including Saturday mornings.
Please call (03) 9704 4744 to make a booking and find the closest testing centre.
How much does each test cost?
None of the tests are covered by Medicare so the patient has to pay the full amount. We try to keep the cost of each test to a minimum and currently the cost is $70 for each test, we require Lactulose is performed as a mandatory first test as a quality measure.