目的 检测外泌体 PD⁃L1（ePD⁃L1）在胃癌患者血浆和组织间隙的表达水平，探讨其表达和 临床病理特征关系，评估其在胃癌中的诊断价值。方法 选取 2021 年 12 月至 2022 年 12 月我院收治的胃 癌患者 40 例，健康对照 20 例。纯化鉴定血浆外泌体，使用酶联免疫吸附测定（ELISA）血浆 ePD⁃L1 的表 达。同期收集 10 例胃癌组织和癌旁组织，测定组织间隙 ePD⁃L1 表达，验证血浆 ePD⁃L1 来源。分析组织 ePD⁃L1 表达和临床资料间的关系，利用受试者工作（ROC）曲线评价其诊断效能。结果 胃癌患者血浆 ePD⁃L1的表达显著高于健康者（P < 0.001），其高表达与CA19⁃9、肿瘤大小、浸润深度、淋巴结转移、pTNM分 期等相关（P < 0.05）。Pearson相关性分析显示血浆与组织ePD⁃L1的表达呈正相关（r = 0.731 5，P = 0.016 2）。 ROC 曲线分析显示 ePD⁃L1 用于诊断胃癌的曲线下面积（AUC）为 0.796（95%CI：0.658 ~ 0.935，P < 0.001）。 结论 ePD⁃L1 的表达与胃癌进展有关。血浆与组织 ePD⁃L1 表达呈正相关。血浆 ePD⁃L1 对于胃癌具有一 定诊断价值。 

Objective To detect the expression level of exosome PD⁃L1（ePD⁃L1）in the plasma and tissue space of patients with gastric cancer and to explore the relationship between its expression and clinicopatho⁃ logical features，while to evaluate its diagnostic value in gastric cancer. Methods Forty patients with gastric cancer admitted to our hospital from December 2021 to December 2022 and 20 healthy control cases were selected. Plasma exosomes were purified and identified，and plasma ePD⁃L1 expression was determined by enzyme⁃linked immuno⁃ sorbent assay（ELISA）. During the same period，10 gastric cancer tissues and paracancellular tissues were collected to determine the expression of ePD⁃L1 in the intertissue space and verify the origin of plasma ePD⁃L1. The relation⁃ ship between ePD⁃L1 expression and clinical data was analyzed，and the diagnostic efficacy of EPD⁃L1 was evaluat⁃ ed by receiver operating（ROC）curve. Result Plasma ePD⁃L1 expression in gastric cancer patients was signifi⁃ cantly higher than that in healthy patients（P < 0.001），and its high expression was significantly correlated with CA19⁃9，tumor size，invasion depth，lymph node metastasis，and pTNM staging（P < 0.05）. Pearson correlation analysis showed a significant positive correlation between ePD⁃L1 expression in plasma and tissue（r = 0.7315，P = 0.0162）. The area under ROC curve（AUC）was 0.796（95%CI：0.658 ~ 0.935，P < 0.001）. Conclusion The expression of ePD ⁃L1 is associated with the progression of gastric cancer. There is a positive correlation between plasma and tissue ePD⁃L1 expression. Plasma ePD⁃L1 has certain diagnostic value in gastric cancer.