The goal of this cross-sectional study is to evaluate the efficacy of current infection marker (CIM) method for H. pylori detection. The main questions it aims to answer are:

• To evaluate the efficacy of CIM method for H. pylori detection compared to rapid urease test(RUT), histopathology, polymerase chain reaction (PCR), and urea breath test (UBT) in patients who presented with upper gastrointestinal hemorrhage from peptic ulcer, and their sensitivity, specificity, accuracy, positive predictive value (PPV), negative predictive value (NPV), positive likelihood ratio, and negative likelihood ratio.
• To evaluate the advantages of CIM method for H. pylori detection comparing to RUT, histopathology, PCR, and UBT in patients who presented with upper gastrointestinal hemorrhage from peptic ulcer as net reclassification index (NRI).
• To study the associated factors in false negative value of H. pylori detection methods with CIM, RUT, histopathology, PCR, and UBT.

Helicobacter pylori (H. pylori) is a Gram-negative bacillus that involves gastric mucosa and was first isolated in 1982. The global prevalence of H. pylori infection is about 50% and the prevalence is different in each region of the world. The highest prevalence of H. pylori infection is up to 70.1% in Africa, but the prevalence in the South-East Asian region varies from 28.6 to 70.3%. For Thailand, the prevalence of H. pylori infection was reported approximately 43.6-64.0%. H. pylori infection is also well-known to be associated with gastric cancer, Gastric mucosa-associated lymphoid tissue (MALT) lymphoma, and peptic ulcer.

Peptic ulcer strongly associates with H. pylori infection. The global prevalence of H. pylori infection is 48.5-94.5% and 66.9-95.8% in gastric ulcer and duodenal ulcer, respectively. These data corresponded to the prevalence in Thailand which is 68.9% and 82.8 % in gastric ulcers and duodenal ulcers, respectively. Peptic ulcer is also one of the common causes of upper gastrointestinal hemorrhage. In contrast, H. pylori eradication has been shown to reduce the risk of recurrent upper gastrointestinal bleeding.

Nowadays, there are several tests for H. pylori infection including endoscopic-based methods such as rapid urease test (RUT), histopathology, culture, and polymerase chain reaction (PCR) for deoxyribonucleic acid (DNA) of H. pylori detection, and non-invasive methods, including urea breath test (UBT), fecal antigen test, and serologic test. In clinical practice, patients under upper gastrointestinal endoscopy with suspicion of H. pylori infection are almost always tested with RUT and histopathology. Both these methods are simple and available with high sensitivity and specificity that is greater 90 and 95%, respectively.

Patients presented with upper gastrointestinal bleeding are recommended to be diagnosed and treated with endoscopy, if the peptic ulcer including gastric ulcer or duodenal ulcer was found, the H. pylori infection must be considered to test. Blood in the gastric cavity, proton pump inhibitor (PPI), and antibiotic prescription can decrease the sensitivity and specificity of RUT and histopathology. Moreover, the patients with gastric ulcer and duodenal ulcer should be generally treated with PPI for a total duration of 8 to 12 weeks and 4 to 8 weeks, respectively, which could affect the accuracy of RUT for H. pylori detection. Although PCR technique has more than 98% of sensitivity, specificity, and accuracy, it is very expensive test that requires high performance center, so PCR test is not always available and not suitable for clinical practice. Therefore, these limitations can delay the diagnosis of H. pylori infection in patients with upper gastrointestinal hemorrhage, so the patients are also not treated this infection in timely manner.

Serology test for H. pylori infection is the test for blood immunoglobulin G (IgG) detection that has 85% sensitivity and 79% specificity 26. PPI or antibiotic uses and upper gastrointestinal bleeding do not affect to this test, so this method might be a better test for H. pylori infection than the endoscopic-based tests including RUT or histopathology. Currently, the immunochromatographic test is a novel method for H. pylori infection that identify current infection marker (CIM) of H. pylori. It is a simple and rapid test in which the sensitivity and the specificity in general population are 90 - 92.3% and 89 - 90.5%, respectively. However, the use of CIM for H. pylori infection in patients with upper gastrointestinal hemorrhage from peptic ulcer who are treated with PPI or antibiotic has not been done yet.

This study aims to evaluate the efficacy of CIM for H. pylori infection test in patients with upper gastrointestinal hemorrhage from peptic ulcer compared to rapid urease test, histopathology, PCR for H. pylori detection, and UBT method.

Inclusion Criteria:

• Age ≥ 18 years
• Upper gastrointestinal hemorrhage and undergo esophagogastroduodenoscopy with diagnosis of peptic ulcer

Exclusion Criteria:

• Inappropriate gastric mucosal biopsy conditions such as hemodynamic instability, coagulopathy or severe thrombocytopenia or massive bloody content in gastric cavity or duodenum
• Previous history of gastric surgery such as partial or total gastrectomy

Patients aged 18 years or older, who present with upper gastrointestinal hemorrhage and undergo esophagogastroduodenoscopy, receiving a diagnosis of peptic ulcer, will be recruited and enrolled. The exclusion criteria include patients with inappropriate gastric mucosal biopsy conditions, such as hemodynamic instability, coagulopathy, severe thrombocytopenia, or the presence of massive bloody content in the gastric cavity or duodenum. Additionally, individuals with a previous history of gastric surgery, such as partial or total gastrectomy, will be excluded.