Colonization with H. pylori is not a disease in and of itself, but a condition associated with a number of disorders of the upper gastrointestinal tract.[13] Testing for H. pylori is recommended if peptic ulcer disease or low-grade gastric MALT lymphoma is present, after endoscopic resection of early gastric cancer, first-degree relatives with gastric cancer, and in certain cases of dyspepsia,[64] not routinely.[13] Several ways of testing exist. One can test noninvasively for H. pylori infection with a blood antibody test, stool antigen test, or with the carbon urea breath test (in which the patient drinks 14C—or 13C-labelled urea, which the bacterium metabolizes, producing labelled carbon dioxide that can be detected in the breath).[64] Also, a urine ELISA test with a 96% sensitivity and 79% specificity is available. None of the test methods is completely failsafe. Even biopsy is dependent on the location of the biopsy. Blood antibody tests, for example, range from 76% to 84% sensitivity. Some drugs can affect H. pylori urease activity and give false negatives with the urea-based tests. The most accurate method for detecting H. pylori infection is with a histological examination from two sites after endoscopic biopsy, combined with either a rapid urease test or microbial culture.[65]
Up to 85% of people infected with H. pylori never experience symptoms or complications.[10] Acute infection may appear as an acute gastritis with abdominal pain (stomach ache) or nausea.[3] Where this develops into chronic gastritis, the symptoms, if present, are often those of non-ulcer dyspepsia: stomach pains, nausea, bloating, belching, and sometimes vomiting or black stool.[11][12]
Individuals infected with H. pylori have a 10 to 20% lifetime risk of developing peptic ulcers and a 1 to 2% risk of acquiring stomach cancer.[5][13] Inflammation of the pyloric antrum is more likely to lead to duodenal ulcers, while inflammation of the corpus (body of the stomach) is more likely to lead to gastric ulcers and gastric carcinoma.[14][15] However, H. pylori possibly plays a role only in the first stage that leads to common chronic inflammation, but not in further stages leading to carcinogenesis.[9] A meta-analysis conducted in 2009 concluded the eradication of H. pylori reduces gastric cancer risk in previously infected individuals, suggesting the continued presence of H. pylori constitutes a relative risk factor of 65% for gastric cancers; in terms of absolute risk, the increase was from 1.1% to 1.7%.[16]
H. pylori has been associated with colorectal polyps and colorectal cancer.[17] It may also be associated with eye disease.[18]
Pain typically occurs when the stomach is empty, between meals and in the early morning hours, but it can also occur at other times. Less common ulcer symptoms include nausea, vomiting, and loss of appetite. Bleeding can also occur; prolonged bleeding may cause anemia leading to weakness and fatigue. If bleeding is heavy, hematemesis, hematochezia, or melena may occur.[19]