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).

Tests vary from country to country, so the following information is provided as a rough guide to typical uses of the hydrogen breath test:

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.

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 bacterial 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 is 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 typically caused by an overgrowth of otherwise normal intestinal bacteria.

Other breath tests that can be taken include: Sucrose Intolerance, d-Xylose and Sorbitol.

[edit] External links

• Hydrogen Breath Test information from MedicineNet.
• Hydrogen Breath Test information from the University of Michigan Health System
• Hydrogen Breath Test information from the GP Notebook
• Hydrogen Breath Test Informationcontains articles and abstracts related to various hydrogen breath test studies and information.
• [1]from Dr. Lyle Hamilton, Ph.D - contains information on the principal of breath test as well as extensive references to breath testing.

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