It is estimated that 50% of the developing world population are infected with HPylori organism in the stomach lining. It is the organism responsible for the majority of duodenal ulcers in adults and children. It can cause inflammation of the stomach lining and ulceration and can be picked up by various means.
A blood test simply tells the doctor that you have been exposed to the organism when they look for the antibody to the Helicobacter pylori and does not mean it is causing problems. This should not be relied upon for any clinical judgement as to whether it is causing problems or not. It can be picked up in the faeces now with a special test but again this does not tell you that there might be a problem associated with it as it may just reside in the stomach lining without causing problems. Thirdly it can be picked up by a special breath test but again this is useful to know whether this has been eradicated if it has been treated but is not terribly useful if one is looking to decide whether it is causing problems.
The only way to determine if there is or isn’t active inflammation and problems secondary to the HPylori is to have a look with a gastroscopy. This sometimes is and isn’t required and your doctor will discuss the pros and cons of this approach depending on the specific details of your case.