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13C-UBT Results After Helicobacter Pylori Eradication


Helicobacter pylori infection is the main aetiologic factor in the development of gastritis, gastroduodenal ulcer disease, and gastric cancer. The urea breath test (UBT) is a non-invasive, simple and safe test, which provides excellent accuracy both for the initial diagnosis of H. pylori infection and for the confirmation of its eradication after treatment.

 

The result of each UBT is expressed as delta (d) per thousand of the 13C/12C ratio of the patient compared with the standard. The precise choice of the cut-off point for this d value to define whether the UBT is positive or negative, however, represents a controversial issue. The cut-off value for the UBT was originally determined as 5.0&, and it has been traditionally most widely recommended. More recently, some authors showed that this cut-off value could be lowered to 3.0 or 3.5& without compromising the sensitivity and specificity of the test, and even improving its accuracy. The selected cut-off point may depend on several factors, such as the dose of urea administered, or the indication of the UBT, and it has been suggested that selection of a lower cut-off value after eradication therapy has been prescribed (in comparison with the pre-treatment setting) may be helpful to maintain the diagnostic accuracy of UBT for monitoring the H. pylori eradication.

 

Other authors have considered a ‘grey zone’ in which the results of UBT are inconclusive, to account for the spontaneous variation of 13CO2 in breath and the limits of the isotope ratio mass spectrometer analytical precision. It has been suggested that a borderline UBT δ value (e.g. very close to the selected cut-off point) should be cautiously interpreted, and the result should probably be confirmed, either by repeating the UBT or by other diagnostic methods. This suggestion is supported by some studies, which have demonstrated that the value of the UBT after treatment is higher in those patients who suffer a recurrence of H. pylori infection. However, no study up to now has prospectively and systematically followed patients withδvaluesclose to the standard cut-off point to assess whether such values change -increase or decrease- with time.

 

At one of the studies ofSpain, The commercially available 13C-UBT KIT (Isomed, S.L., Madrid,Spain) was used. It was indicated that although a unique and generally proposed UBT cut-off level is not possible because it has to be adapted to different factors, such as the test meal, the dose and type of urea, or the pre/post-treatment setting in which the test is employed, fortunately, because positive and negative UBT results tend to cluster outside of the range between 2 and 5‰, contrary, a δ UBT value <2‰ very confidently confirms H. pylori eradication.


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