These require a tiny specimen of the stomach lining called a biopsy, which is taken during an endoscopy. The specimen is placed in a special solution (either liquid or gel), which changes color if Helicobacter Pylori (H. pylori) is present; this is called a urease test.
H. pylori organisms secret a protein chemical called urease, which converts urea (a substance present in the bloodstream and in urine produced by the breakdown of protein) to ammonia. The diagnostic solutions contain urea and an alkali indicator. If H. pylori is present within the biopsy, placed in the test solution then the urea is converted into ammonia, which causes the alkali indicator to change color, thus producing a positive test.
Depending on which test solution used, the result takes from a few minutes to 24 hours to become available. In addition to the urease test, the biopsy specimen can also be sent to the pathology department to be looked at under the microscope. Not only can the rnicroscopic H. pylori themselves be seen in this way but so can the associated microscopic stomach inflammation called gastritis.
The main advantage of these tests is that they are the most accurate available and confirm whether or not active H. pylori is present at the time of the test. In addition, while performing the endoscopy, the doctor can see if there is anv evidence of a peptic ulcer, suggesting that H. pylori should be eradicated.
The disadvantage of tissue testing is that it requires an endoscopy, but looking for H. pylori is rarely the only reason for doing such an investigation, so it makes sense to do a biopsy at the same time anyway. In common with some other H. pylori tests, the results can be incorrectly interpreted if you are taking a type of medication called a proton pump inhibitor (such as omeprazole, lansoprazole or pantoprazole), which suppresses the bacterium without actually killing it.