[Analysis of the gray-zone cutoff values of new serum Helicobacter pylori antibody kits using latex immunoassay].

The serum Helicobacter pylori titers are good markers for population-based H. pylori screening and treatment programs because the tests used to estimate these titers are noninvasive, inexpensive, and convenient. However, the reference range of 3-10U/mL, which is used as a standard in commercially available serum H. pylori antibody kit E plate Eiken H. pylori antibody II, is regarded as a gray-zone cutoff value to indicate H. pylori infection status. We aimed to clarify the gray-zone cutoff values of H. pylori infection status with new serum H. pylori antibody kits using latex immunoassay. We enrolled 256 patients who underwent endoscopic examination and H. pylori tests at the Inui Clinic of Internal Medicine or IMS Ota Central General Hospital between January 2013 and December 2015. Serum H. pylori titers were measured using Type L Wako H. pylori antibody J (Wako-LIA), H. pylori-latex Seiken (Denka-LIA), and LZ test Eiken H. pylori antibody (Eiken-LZ). In patients with a positive diagnosis of H. pylori infection, the positive diagnostic values (sensitivity, specificity, and positive predictive value) using Wako-LIA, Denka-LIA, and Eiken-LZ were (94.6%, 86.0%, and 79.1%), (95.7%, 90.2%, and 84.6%), and (85.9%, 92.1%, and 85.9%), respectively;in patients with a negative diagnosis of H. pylori infection, the diagnostic values (sensitivity, specificity, and negative predictive value) using Wako-LIA, Denka-LIA, and Eiken-LZ were (96.9%, 83.5%, and 85.6%), (96.9%, 78.7%, and 82.2%) and (95.3%, 67.7%, and 75.0%), respectively. In this study, the gray-zone cutoff value indicating H. pylori infection status was between 4.0 and 8.7U/mL for Wako-LIA, between 10.0 and 15.2U/mL for Denka-LIA, and between 5.6 and 10.0U/mL for Eiken-LZ. Therefore, we propose that lower titers of the positive antibody are important to diagnose H. pylori infection using Wako-LIA and Denka-LIA. However, when using Eiken-LZ, high titers of the negative antibody should be considered diagnostically important.