Diagnostic methods in helicobacter pylori infection : development, evaluation and application

University dissertation from Stockholm : Karolinska Institutet, Department of Medicine

Abstract: Aim: To develop, evaluate and apply diagnostic methods for H. pylori infection. Materials and Methods: An in-house Urea Breath Test (UBT) was developed and evaluated in three different settings, using serology by ELISA and immunoblot as gold standard. Further, the Heliprobe was evaluated as an alternative diagnostic device. The UBT results in both studies were evaluated on consecutive patients referred to UBT due to either primary H. pylori screening or posttreatment evaluation. Sera from Swedish and Vietnamese patients and population control were used to compare the diagnostic performance of commercially available diagnostic kits and an inhouse ELISA. Luminal gastric nitric oxide (NO) was measured during endoscopy sessions along with biopsies harvested for histology and culture assessment. Sera were drawn for ELISA and immunoblot to establish H. pylori virulence factor status. H. pylori infection and gastrointestinal haemorrhage in patients with bleeding disorders in Sweden and Estonia was investigated. Diagnostic serology followed by UBT was used for screening purposes. All infected patients received eradication treatment, and were evaluated for gastrointestinal bleeding, comparing the five years prior to eradication with the ensuing 3.3 years. The costs involved with H. pylori screening, eradication and gastrointestinal bleeding events were determined. Results: The inhouse UBT was refined with reduced amount of radioactivity and the use of citric acid to enhance accuracy. The sensitivity and specificity was 93% and 100% respectively. The Heliprobe test results displayed 100% concordance with the in-house UBT. The in-house ELISA showed a significantly better performance if based on local strains. Due to lower antibody titres in Asian asymptomatic infected patients the kits required adjustment of cut-off limits for screening and seroepidermological purposes. The luminal gastric levels of NO were significantly increased in H. pylori infected patients as compared to non-infected. A trend towards higher NO levels was found in patients with acute inflammation in gastric mucosa. In patients with bleeding disorders the incidence of gastrointestinal bleeding was reduced from 6 to 1.7 per 100 patient years. H. pylori screening and eradication reduced the medical costs involved. Conclusions: The in-house and Heliprobe UBT are appropriate diagnostic tools for detecting H. pylori. Serological H. pylori diagnostics based on ELISA needs evaluation and adjustment according to target populations. Luminal gastric NO levels indicate inflammation due to H. pylori infection. Screening and eradication of H. pylori infection in patients with bleeding disorders is an effective and economic strategy.

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