The OLGA staging system classifies the stage of gastritis based on the extent and location of gastric atrophy identified through biopsy samples from five sites. Stages are determined by combining the histological severity of atrophy with its topographic distribution, with higher stages being more strongly associated with gastric cancer risk. Initially developed in 2006, OLGA aims to standardize gastritis reporting and risk assessment internationally. Studies have found OLGA staging useful for predicting progression to neoplasia and tailoring endoscopic surveillance strategies.