Pepsinogen I(PGI) Determination Reagent(Latex Immunoturbidimetry) is an in vitro diagnostic quantitative test kit. Pepsinogen is an inactive precursor of pepsin (proteolytic enzyme) in gastric juice, which is divided into pepsinogen I and pepsinogen II by immunoassay. PG I is secreted by fundic glands, and PG II is secreted by fundic glands, cardia glands, pyloric glands, and Brunner's glands. In the process of fundic gland mucosal atrophy, the main cells secreting PG I decrease, and the pyloric gland cells increase. The PG I/PG II ratio decrease. Therefore, PG I/PG II ratio can be used as an indicator of fundic gland mucosal atrophy, and the determination of PG I and PG II combined with PG I/PG II ratio can be used to screen fundic gland mucosal atrophy, especially atrophic gastritis. This kit is used for auxiliary diagnosis of atrophic gastritis and other gastrointestinal diseases such as ulcer.