CARBON-13 (13CO2) BREATH TESTING
Carbon-13 breath tests have been used in gastrointestinal research
for many years as safe, simple and non-invasive methods of monitoring organ function
and nutritional status. They have been employed in study of gastric emptying, liver
function, fat absorption, P450 mixed-function oxidase, bacterial overgrowth, oro-caecal
transit time, etc.
Iso-Analytical provides a comprehensive mass spectrometry
service for carbon-13 breath test samples and also can offer help in experimental design
and data interpretation.
In simple terms, carbon-13 breath tests involve the ingestion
of a substrate (commonly used substrates include: acetate, caffeine, erythromycin,
octanoic acid, urea, triglyceride or xylose) labeled on one or more functional groups
with 13C. These 13C labeled functional groups are cleaved from the rest of the substrate
molecule by the action of specific enzymes. The functional groups then further oxide
until 13C enriched CO2 is produced and excreted in breath and the 13C:12C ratio in
serially collected breath samples is measured by isotope ratio mass spectrometry.
See Example Laboratory Report for 13C-Urea breath tests to detect Helicobacter pylori infection.
Liver Function Breath Tests
Historically, blood tests and scoring indexes have
been employed to identify and monitor patients with liver disease. These tests
reflect end point hepatocellular damage but do not quantitate functional hepatic
reserve. Thus whilst advanced liver disease can be diagnosed with confidence,
early or marginal hepatic disease is poorly defined. To increase this definition
a series of breath tests have been developed and refined over the last 20 years.
Specific liver function breath tests targeted at exploring the functionality of
cytosolic, microsomal and mitochondrial enzyme systems within the hepatocyte are
available. These tests provide information on:
prediction of long term prognosis
monitoring the progression of liver disease
following the effects of a therapeutic regimen
decision in optimum transplant timing
Gastric Emptying Breath Tests
Breath tests offer an alternative to scintigraphic techniques for measuring gastric
emptying. The rate of emptying can be determined with 13C labeled octanoate
(solid food) or acetate (liquid meals). The safety of the carbon-13 breath test
and the ability to use it repeatedly has meant that it has found favour by those
wanting to assess the efficiency of new motility drugs.
Bacterial Overgrowth Breath Tests
breath test offers a diagnostic alternative to the microbiological analysis
of jejunal fluid for the diagnosis of small bowel bacterial overgrowth.
This test offers a practical way of serial testing a condition that is often
persistent throughout life.
Oro-Caecal Transit Time Breath Tests
has proven to be a reliable marker to follow oro-caecal transit time.
The tracer resists the action of brushborder enzymes and is not metabolised
until reaching the colonic bacteria.
Other Breath Tests
There are a number of other breath tests that are used in
gastrointestinal research. These include:
Erythromycin breath test
(cytochrome P450 1A4 activity)
13C-Caffeine breath test (cytochrome P450 1A2 activity)
test (Helicobacter pylori infection)
13C-Mixed triglyceride breath test (pancreatic function)
digestion breath test (lactose intolerance)
For further information please
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