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.

Objective Helicobacter pylori antibody kits using the latex immunoassay (LIA) are widely used in Japan. However, the optimal cut-off of the LIA remains unclear. This study clarified the optimal cut-off of the LIA for assessing the current infection status of patients (currently infected, never infected, spontaneously eradicated) in clinical practice. Methods In total, 482 subjects with no history of H. pylori eradication therapy who underwent a medical examination at our hospital were enrolled. The infection status was ascertained using a stool antigen test, and the endoscopic findings of H. pylori-associated gastritis. H. pylori antibody levels were measured using the LIA. Results In total, 414, 38, and 30 subjects were categorized into the never-infected, currently infected, and spontaneously eradicated groups. The optimal cut-off based on receiver operating characteristic curve analysis was 4 U/mL, whereas the area under the curve, sensitivity, and specificity for differentiating never-infected and currently infected subjects were 0.95, 92.1%, and 94.7%, respectively. When applying the cut-off of 4 U/mL to the judgment of current infection in all subjects, the sensitivity and specificity were 92.1% and 92.6%, respectively. Conclusion Our findings suggest that 4 U/mL was the optimal cut-off for differentiating current infection from no prior infection, and the value may be stable because of the exclusion of subjects with spontaneous eradication. The cut-off may be useful in initial screening for current H. pylori infection.