Most studies conclude that it is difficult to diagnose H. pylori related gastritis and gastric atrophy on the basis of endoscopic findings. Histology is therefore currently considered to be the gold standard for detecting H. pylori infection. The reliability of detecting H. pylori infection histologically depends on the site, number, and size of gastric biopsy specimens, as well as on expertise in staining and visualizing the bacteria. Considerable error also occurs in identifying gastric atrophy using blind biopsy sampling, and neither the original nor the revised version of the Sydney system reliably identifies more than half the cases in patients with confirmed gastric atrophy.