Diagnosis of Helicobacter pylori infections

In children, an ulcer is rare and less specific symptoms can be observed: abdominal pain, iron deficiency anaemia and thrombocytopenic purpura. In terms of epidemiology, the stomach of humans and primates is the reservoir for this bacteria and human-to-human contamination occurs in a faecal-oral and oral-oral manner.

Once the bacteria enters into the body, it provokes an inflammatory reaction of the gastric mucosa with both a tissue and humoral immune response. Amongst those suffering from such an infection, only 1-2% develop symptoms. The gastritis can remain stable or develop further to become an ulcer or evoke mucosal atrophy and a adenocarcinoma. It has been noted that over 90% of those with a gastroduodenal ulcer are infected with H. pylori.

The indications for the screening of Helicobacter pylori are listed in the Maastricht IV consensus report (2010) and are as follows:

The screening and biological diagnosis relies on both invasive and non-invasive methods.

Among the non-invasive methods, the breath test relies on the urease activity of this bacteria and measures this activity in the patient’s expired breath via mass spectrometry analysis of the different proportions of C13/C12 before and after ingestion of labelled urea. To perform this test, the patient must stop all antibiotic treatments one month prior to examination and stop proton pump inhibitors (PPI) 15 days prior to examination.

• The detection of antigens in stool samples is reserved for the monitoring of patient progress following treatment in order to verify the eradication of Helicobacter pylori (except in children, where this test can be used as a screening technique).
• Serology testing does not distinguish between a recent past infection because it does not detect IgM (too transient). It detects IgG antibodies which are associated with the infection but appear relatively late in the infection (3 weeks after initial infection) and remain raised throughout the duration of the infection. They return to a normal level after approximately 1 year. Furthermore, asymptomatic Helicobacter pylori carrier patients have a positive serology result and represent 50% of the adult population. Its positivity several months following eradication means it cannot be used as a tool for post-treatment verifications. Its indications are therefore limited to digestive bleeding, gastric atrophy, MALT lymphomas and gastric carcinoma as the bacterial inoculum is weak in this clinical setting, thus compromising the use of other laboratory tests.

The invasive methods are performed on biopsy fragments collected from the gastric antrum and gastric fundus during a gastroduodenal fibroscopy. At the same time, the biopsies are crushed and cultured under microaerophilic conditions for 12 days. This micro-organism of often fastidious growth can also be screened for using PCR analysis on biopsy samples, which allows for simultaneous screening of clarithromycin and fluoroquinolone resistance genes. The therapeutic approach must differ according to whether the patient lives in a zone with a high incidence or low incidence of cancer. In high incidence zones, systematic eradication of this bacteria is clinically justified. In low incidence zones, such as France, it seems reasonable, in asymptomatic cases, to reserve the screening of Helicobacter pylori infection and pre-neoplastic lesions for patients with a high-risk of developing cancer.

References

• Malfertheiner P, Megraud F, O’Morain C, Bazzoli F, El-Omar E, Graham D, et al.
  Current concepts in the management of Helicobacter pylori infection – The Maastricht III Consensus Report.
  Gut 2007.
• Cambau E, Allerheiligen V, Coulon C, Corbel C, Lascols C, Deforges L, et al.
  Evaluation of a new test, genotype HelicoDR, for molecular detection of antibiotic resistance in Helicobacter pylori.
  J Clin Microbiol 2009;47(11):3600-7.
• Graham DY, Fischbach
  L. Helicobacter pylori treatment in the era of increasing antibiotic resistance.
  Gut 2010;59(8):1143-53.

Table 1 : performance of non-invasive methods

Table 2 : performance of invasive methods