CEACAM5 and gastric cancer: ROC curve analysis showed that the AUC value of circPTPN22 (0.787, 95% confidence interval: 0.723–0.851, P < 0.001) is higher than CEA (0.701, 95% confidence interval: 0.616–0.786, P < 0.001) and CA199 (0.695, 95% confidence interval: 0.614–0.776, P < 0.001) (Fig. 3e) in distinguishing GC and gastritis, and the sensitivity was also significantly increased after combined diagnosis, with the AUC value of circPTPN22 is 0.817 after combined use with CEA, 0.833 after combined use with CA199, and The AUC value of the three is 0.856 after combined use (Fig. 3f).