The Optimal Cut-off of the Latex Immunoassay (LZ Test) for Helicobacter pylori Infection Based on the Stool Antigen Test and Helicobacter pylori-associated Gastritis

Diagnostic Accuracy of a Novel Stool Antigen Test for Helicobacter pylori Infection in a Medical Checkup Setting: A Prospective Cohort Study

Objective Of the highly accurate tests for current Helicobacter pylori infection, the urea breath test (UBT) and stool antigen test (SAT) are noninvasive and do not require endoscopy. We conducted a prospective study to evaluate the accuracy of the newly developed SAT in a medical checkup setting. Methods The accuracy of the proposed SAT was examined by determining H. pylori infection status based on a history of eradication therapy, endoscopic H. pylori infection diagnosis, and blood tests (serum H. pylori antibody, serum PG II) in individuals undergoing esophagogastroduodenoscopy (EGD) during a health checkup. Results The new SAT showed 97.3% (108/111) sensitivity for those "currently infected," as well as 99.3% (530/534), 98.0% (402/410), and 98.7% (932/944) specificity for those "never infected," those "previously infected," and those "never/previously infected", respectively. Conclusion The newly developed H. pylori SAT may be useful for diagnosing H. pylori infection. Patients should be suspected of being infected even after H. pylori eradication if they have a high cutoff index in this test.

A novel predictive formula for highly accurate discrimination between truly Helicobacter pylori-uninfected and currently infected/spontaneously eradicated individuals for gastric cancer screening

The ABC classification, which categorizes gastric cancer risk based on serum Helicobacter pylori (H pylori) antibody and pepsinogen levels, has a limitation of potentially misclassifying high-risk individuals as low risk. To overcome the problem, we previously developed a 4-parameter predictive formula (age, serum H pylori antibody, PGI, and PGII) using logistic regression analysis to accurately identify low-risk truly H pylori-uninfected status. Our predictive formula demonstrated superior sensitivity and specificity in distinguishing between low-risk truly uninfected individuals and high-risk currently/spontaneously eradicated status individuals, compared to the modified ABC classification based on latex immunoassay kits (traditional 3-parameter model). This study aimed to revalidate the diagnostic accuracy of the predictive formula in a new and different study population. We applied the predictive formula to the target population and compared the sensitivity and specificity with those of the traditional 3-parameter model. A total of 788 enrollees were analyzed: 703 were classified as truly uninfected, 45 as currently infected, and 40 as spontaneously eradicated according to the results of stool antigen testing and endoscopic findings. The sensitivities and specificities of the predictive formula and the traditional 3-parameter model were 89.5% and 87.1% versus 89.8% and 80.0%, respectively. The specificity of the predictive formula was superior in the 70 to 89 age range and H pylori antibody < 3 U/mL groups. The predictive formula had higher specificity than the traditional 3-parameter model. The results should contribute to efficient gastric cancer screening by predicting H pylori infection status.