Abstract: Objective To explore and analyze the diagnostic value of microRNA-26a (miR-26a) and microRNA-663 (miR-663) combined with Helicobacter pylori in the diagnosis of precancerous lesions in elderly patients with gastric cancer. 
Methods In total, 136 elderly patients with benign gastric lesions, precancerous lesions or early gastric cancer who were admitted to our hospital and diagnosed by gastroscopic and pathological examinations were consecutively selected as the research subjects. The expression of serum miR-26a and miR-663 was detected by real-time fluorescence quantitative polymerase chain reaction (RT-qPCR), and the positive status of Helicobacter pylori was detected by 13C urea breath test. The diagnostic value of miR-26a, miR-663, and Helicobacter pylori detected alone and in combination for different degrees of gastric benign lesions, precancerous lesions and early gastric cancer was analyzed, and the receiver operating characteristic (ROC) curve was drawn to evaluate the diagnostic accuracy. 
Results There were no significant differences in gender, age, body mass index, smoking history, and drinking history among patients with benign gastric lesions, precancerous lesions, and early gastric cancer (P＞0.05), and the family history of gastric cancer in patients with gastric precancerous lesions and early gastric cancer was higher than that in patients with benign lesions (P＜0.05). There was no significant difference in the family history of gastric cancer between patients with precancerous lesions and early gastric cancer (P＞0.05). The expression levels of serum miR-26a and miR-663 in patients with gastric precancerous lesions and early gastric cancer were lower than those in patients with benign gastric lesions, and the serum miR-26a and miR-663 expression levels in patients with early gastric cancer were lower than those in patients with precancerous lesions, while the positive rate of Helicobacter pylori was higher than that in patients with benign gastric lesions(P＜0.05). There was no significant difference in the positive rate of Helicobacter pylori between patients with precancerous lesions and early gastric cancer (P＞0.05). The sensitivity of combined detection of the three was significantly higher than that of miR-26a detection alone （χ2=4.680，P=0.031）, miR-663 detection alone （χ2=8.223，P=0.004）, and Helicobacter pylori detection alone （χ2=6.363，P=0.012）. When the cut-off value of serum miR-26a was 2.63, the area under the ROC curve (AUC) for diagnosing precancerous lesions in elderly patients with gastric cancer was 0.79 (95%CI: 0.774-0.856), and the sensitivity and specificity at this time were 75.43% and 79.85%, respectively. When the cut-off value of serum miR-663 was 4.35, the AUC for the diagnosis of precancerous lesions in elderly patients with gastric cancer was 0.83 (95%CI: 0.796-0.875), and the sensitivity and specificity were 81.37% and 78.56%, respectively. The AUC of Helicobacter pyloriin the diagnosis of precancerous lesions in elderly patients with gastric cancer was 0.72 (95%CI: 0.648-0.769), and the sensitivity and specificity were 68.93% and 78.45%, respectively. The AUC of the combined detection of the three above indicators in the diagnosis of precancerous lesions in elderly patients with gastric cancer was 0.89 (95%CI: 0.815-0.873), and the sensitivity and specificity were 89.72% and 74.43%, respectively. 
Conclusion miR-26a, miR-663 combined with Helicobacter pylori has high diagnostic value for the precancerous lesions of gastric cancer in the elderly, and the combined diagnosis helps to improve the diagnostic sensitivity, thereby providing guidance for the early diagnosis of gastric cancer in the elderly.  

Key words: Helicobacter pylori, precancerous conditions, diagnosis