Hydrogen Breath Test (cont.)
How is hydrogen breath testing performed?
Prior to hydrogen breath testing, the patient fasts for at least 12
hours. At the start of the test, the patient blows into and fills a balloon with
a breath of air. The concentration of hydrogen is measured in a sample of breath
removed from the balloon. The patient then ingests a small amount of the test
sugar (lactose, sucrose, sorbitol, fructose, lactulose, etc. depending on the
purpose of the test). Additional samples of breath are collected and analyzed
for hydrogen every 15 minutes for three and up to five hours.
How are the results of hydrogen breath testing
interpreted?
The interpretation of the results of hydrogen breath testing depends
on the sugar that is used for testing, and the pattern of hydrogen production
after the sugar is ingested.
After ingestion of test doses of the dietary sugars lactose, sucrose,
fructose or sorbitol, any production of hydrogen means that there has been a
problem with digestion or absorption of the test sugar and that some of the
sugar has reached the colon.
When rapid intestinal transit is present, the test dose of non-digestible
lactulose reaches the colon more quickly than normally, and, therefore, hydrogen
is produced by the colonic bacteria soon after the sugar is ingested.
When bacterial overgrowth of the small bowel is present, ingestion of
lactulose results in two separate periods during the test in which hydrogen is
produced, an earlier period caused by the bacteria in the small intestine and a
later one caused by the bacteria in the colon.
What are the limitations of hydrogen breath
testing?
There are several limitations to hydrogen breath testing. For unclear
reasons, testing for bacterial overgrowth of the small bowel with lactulose can
diagnose only 60% of cases. (This insensitivity of the test may be due in part
to the strict criteria that are used for interpreting a test as abnormal. Less
strict criteria may diagnose overgrowth more often.) In addition, with bacterial
overgrowth there may be an overlap of the early and later periods of hydrogen
production that can be misinterpreted as a single period characteristic of rapid
intestinal transit. Finally, some normal individuals may have slow transit
through the small intestine making prolonged testing - up to 5 hours -
necessary, and many individuals are unwilling to undergo such prolonged testing.
Some individuals do not have bacteria that produce hydrogen, and in these
individuals hydrogen breath testing is not possible. Most of these individuals
have bacteria that produce a different gas, methane. (There also are individuals
who produce both hydrogen and methane.) Methane can be measured in the breath
just like hydrogen, and the production of methane can be used for diagnosis in
the same way as hydrogen. There is much less experience with methane, however,
and the production of methane is more complex than the production of hydrogen.
Therefore, it is not clear if the pattern of methane production after ingestion
of sugars can be interpreted in the same way as hydrogen production,
particularly for the diagnosis of bacterial overgrowth.
A pattern of hydrogen production that is typical for bacterial overgrowth
does not necessarily mean that an individual's symptoms are caused by the
overgrowth. For example, there may be anatomic abnormalities of the small
intestine such as narrowing or functional abnormalities in the way the
muscle of the small intestine works. These abnormalities can cause symptoms
of bloating, distention, pain,
and diarrhea themselves, but they also can lead to bacterial overgrowth with its
similar symptoms. Therefore, it may be an underlying abnormality that is
responsible for the symptoms and not the bacterial overgrowth. The only way to
differentiate between the two causes of symptoms-an underlying problem or
bacterial overgrowth - is to treat and eradicate the bacteria. If the symptoms
disappear, then it is more likely that it is the overgrowth rather than the
underlying abnormality that is responsible for the symptoms.
Any condition that results in the delivery of undigested or unabsorbed food
to the colon may result in abnormal breath tests when dietary sugars are used
for testing. Both pancreatic
insufficiency and celiac sprue
can cause abnormal breath tests, in the former instance because pancreatic
enzymes that are necessary for the digestion of carbohydrates are missing,
and in the latter instance because the lining of the small intestine is
destroyed, and digested food cannot be absorbed. It may be necessary to exclude
these causes of abnormal breath tests by additional tests-pancreatic function
tests and small intestinal biopsy.
Next: Are there other ways in which hydrogen breath testing can
be used? »
- Colonoscopy - Learn about the colonscopy procedure, what it is, why it is performed, preparation, complications, alternatives and the after effects of the screening exam on MedicineNet.com
- Abdominal Pain - Learn about abdominal pain (pain in the stomach / abdomen) including causes, symptoms, how abdominal pain is diagnosed, and how abdominal pain is treated.
- Endoscopy (Esophagogastroduodenoscopy, EGD) - Learn about the endoscopy procedure which examines the esophagus, stomach and duodenum to detect gastrointestinal and digestive disorders on MedicineNet.com
Latest Medical News
Digestion RSS