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H Pylori Breath Test

Helicobacter pylori breath tests work by having the patient drink a liquid containing urea enriched with the carbon isotope C-13. H. pylori bacteria in the stomach produce urease which breaks down urea into ammonia and carbon dioxide. The carbon dioxide, including any C-13, enters the bloodstream and is breathed out. If tests of the breath afterward find elevated levels of C-13 compared to before, it indicates the presence of urease-producing H. pylori bacteria in the stomach. A difference of over 3.5 parts per 1000 is considered a positive result, with higher levels corresponding to more severe infections.

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Sanjay Navale
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126 views1 page

H Pylori Breath Test

Helicobacter pylori breath tests work by having the patient drink a liquid containing urea enriched with the carbon isotope C-13. H. pylori bacteria in the stomach produce urease which breaks down urea into ammonia and carbon dioxide. The carbon dioxide, including any C-13, enters the bloodstream and is breathed out. If tests of the breath afterward find elevated levels of C-13 compared to before, it indicates the presence of urease-producing H. pylori bacteria in the stomach. A difference of over 3.5 parts per 1000 is considered a positive result, with higher levels corresponding to more severe infections.

Uploaded by

Sanjay Navale
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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How Does it Work?

Helicobacter pylori breath tests

H pylori diagnostic breath tests rely on a sim- the extent of the infection. Levels of 30-40
ple chemical reaction which is based on the parts per 1000 over the baseline result are
natural behaviour of the bacteria. Naturally typical of H pylori infections.
occuring gastric urea is made up of 99% car-

r pylori
bon isotope 12C and 1% carbon isotope 13C.
The breath test uses urea enriched with 13C

b a cte
(that is, 99%).

Helio
r pylori

2 H pylori survives in gastric acid by excreting large


amounts of urease. This enzyme breaks down any
b a cte

urea in the stomach to ammonia and carbon dioxide


4 The carbon dioxide is absorbed into the blood
Helio

stream and then released from the lungs


pylori. The enriched urea provided by the
testing kit must have been broken down to
Two back-up tubes are generally also
produce high levels of 13C in the breath and
taken at baseline and post-dose stages.
this implies the presence of urease excreting
The sensitivity of such diagnostic kits is
1 Virtually all duodenal ulcers and 80% of gastric H pylori in the stomach.
96% and the specificity is 100%.
ulcers are associated with Helicobacter pylori
infections1
1 Graham DY. Helicobacter pylori infection in the pathogen-
esis of duodenal ulcer and gastric cancer: a model. Gastro-
Patients first drink a sachet of orange enterology 1997; 113(6):1983-91
juice or citric acid. This rapidly closes the
r pylori

duodenal sphincter to contain the stomach Abi Berger, science editor, BMJ
contents. They are then asked to blow
b a cte

through a straw into a glass tube with a Naturally Breath


screw cap lid. This provides the baseline
Helio

occuring test urea


sample. urea enriched with...
Next, they consume a drink containing
99% carbon isotope C

99% carbon isotope C


13
C enriched urea (about 100 ml) and after
1% carbon isotope C
12

13
30 minutes repeat the blowing exercise into
13

a second tube. This provides the post-dose 3 The ammonia neutralises any acid found directly in
sample. Both samples are sent away for car- the vicinity of the bacteria, allowing the bacteria to
bon dioxide isotope analysis by mass survive
spectrometry (laboratories usually return
the results within a few days). If the post-dose 13C concentration is 3.5
The level of 13C in the baseline sample parts per 1000 more than the baseline sam-
will be normal. If levels rise in the post-dose ple, the test is considered positive for H
sample, this suggests the presence of H pylori. The higher the level of 13C, the greater

BMJ VOLUME 324 25 MAY 2002 bmj.com 1263

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