Editing Helicobacter pylori (section)

== '''Invasive tests''' ==

* Urease assay/Rapid urease     test/CLO test
** Use four endoscopic biopsy      specimens from gastric body and antrum
** Test specimens for urease.      If Helicobacter is present, urease will hydrolyse the urea in the sample      well to ammonium, causing a rise in pH and thus a colour change. Any      red/pink/orange is positive, while yellow is negative. Technically needs      24 hours to fully react.
** Sensitivity >90%,      specificity 95-100%
** Lower sensitivity in those      taking PPIs, H2 antagonists, or antibiotics - only worthwhile doing when      it will change management, i.e. you have a high enough suspicion that you      want to start treating right away instead of waiting for histology
* Histology
** Biopsy from both antrum and      body - the organisms tend to migrate proximally with PPI use
** Histologic visualisation of      H. pylori using either routine haematoxylin-eosin stains or other special      stains
** Sensitivity 95%, specificity      99%
** Lower sensitivity in those      taking PPIs, H2 antagonists, or antibiotics
** More expensive than urease      assay
* Culture
** Biopsy specimens obtained at      endoscopy
** Need to take specimen before      forceps are contaminated with formalin
** Sensitivity 80%, specificity      100%
** Takes 3-5 days
** Can do sensitivities