Evaluation of the Anti-East Asian CagA-Specific Antibody for CagA Phenotyping

ABSTRACTThe determination of the cagAgenotype is generally based on sequencing the variable 3' region of the cagAgene. In a previous study, we successfully generated an anti-East Asian CagA-specific antibody (anti-EAS Ab) immunoreactive only with the East Asian CagA and not with the Western CagA. In a small number of Japanese patients, anti-EAS Ab appeared to be a useful tool for phenotyping CagA immunohistochemically. The present study was conducted to validate the anti-EAS Ab immunohistochemistry method in a larger number of patients from Vietnam and Thailand. A total of 385 Vietnamese and Thais were recruited. Helicobacter pyloristatus was determined by a combination of three methods, including culture, histology, and immunohistochemistry with anti-H. pyloriantibody. The sensitivity, specificity, and accuracy of the anti-EAS Ab immunohistochemistry method for the diagnosis of CagA phenotype were calculated based on the results of the cagAsequencing as the gold standard. The sensitivity, specificity, and accuracy of our immunohistochemistry method were 96.7%, 97.9%, and 97.1%, respectively. Moreover, anti-EAS Ab was not cross-reactive with noninfected gastric mucosa. In conclusion, immunohistochemistry with anti-EAS Ab appears to be a good method for determination of CagA phenotype.