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Our aim was to define the utility of breath ammonia measurement in assessing Helicobacter pylori infection. Volunteers breathed into a device containing three fiberoptic NH3 sensors at baseline and after ingesting 300 mg of urea. Breath ammonia levels were compared to the [14C]urea breath test. Thirteen subjects were tested. Before urea ingestion, H. pylori-positive subjects had significantly lower breath ammonia levels than negative subjects (mean SD, 0.04 ppm 0.09 vs 0.49 ppm 0.24, P 0.002) and had a significantly greater increases in breath ammonia after urea ingestion (range 198-1494% vs 6-98%). One H. pylori-positive subject underwent treatment and breath ammonia levels shifted from the pattern seen in positive subjects to that seen in negative subjects. In conclusion, breath ammonia measurement for H. Pylori-positive and negative subjects showed distinct patterns. Breath ammonia measurement may be feasible as a diagnostic test for H. pylori.
KEY WORDS: Helicobacter pylori; ammonia.
The high urease activity of the H. pylori organism has led to the development of diagnostic tests that rely on the presence of urease breakdown products, CO2 and NH3, to serve as an indicator of active infection. Direct measurement of gastric juice urease activity has been proposed as a sensitive and specific means of diagnosing H. pylori infection, but requires an endoscopic procedure (1). Noninvasive breath tests based on CO2, using isotopically labeled [13C]- and [14C]urea have been shown to have excellent test characteristics (2- 8). However, the [13C]urea breath test is relatively expensive and the [14C]urea breath test requires use of a radionuclide that may limit its use in children or pregnant women.
Measurement of ammonia in the breath formed by the action of the H. pylori urease enzyme has received relatively little study in humans. Ammonia is normally present in the breath at very low concentrations of 100-2000 parts per billion (ppb) as part of a complex mixture of volatile organics, making measurement difficult and unreliable with conventional sensors (9).
We sought to assess a novel new fiberoptic ammonia sensor that has the potential to provide a low cost and portable testing modality for breath ammonia. It is known that patients with H. pylori develop elevated gastric juice ammonia levels (1, 10-14). Ammonia is absorbed across the gastrointestinal lumen and converted by the liver...