Abstract: OBJECTIVE：To investigate the usefulness for combined detection of serum miRNA-183 and carbohydrate antigen 199 (CA199) in the diagnosis and prognosis of gastric cancer. METHODS：From January 2017 to December 2021，fifty-two patients with gastric cancer，who were diagnosed in the Affiliated Chuzhou Hospital of Anhui Medical University were selected and their case data were used as the gastric cancer group. In addition，40 patients with benign stomach lesions were included as the non-gastric cancer group. Their levels of serum miRNA-183 and CA199 were determined. RESULTS：Differences in the levels of serum miRNA-183 between the gastric cancer and the non-gastric cancer groups were statistically significant (P<0.05). Expression levels of the serum miRNA-183 in patients with histopathologic classification of low-undifferentiated，T3-T4 and TNM stage III-IV were significantly higher than that in patients with histopathologic classification of medium-highly differentiated，T1-T2 and TNM stage I-II， (P<0.05). Expression levels of the serum CA199 in patients with histopathologic classification of low-undifferentiated and TNM stage III-IV were significantly higher than that in patients with histopathologic classification of medium-highly differentiated and TNM stage I-II， (P<0.05). Using the ROC curve analysis，the optimal cutoff value of the relative expression level of serum miRNA-183 was 4.11. The sensitivity and specificity were 67.31% and 80%，respectively. The area under the curve (AUC) was 0.771. The optimal cutoff value of the relative expression level of serum CA199 was 46.17 U/mL. The sensitivity and specificity were 53.8% and 87.5%，respectively. The area under the curve (AUC) was 0.724. The sensitivity and specificity of combined detection of serum miRNA-183 and CA199 in the diagnosis of gastric cancer were 76.92% and 87.5%，respectively，and the AUC was 0.882. The AUC of miRNA-183 combined with CA199 in diagnosis of gastric cancer was greater than that of miRNA-183 and CA199 independently. Kaplan-Meier analysis showed that the prognosis of patients with high expression of miRNA-183 was worse than that of patients with low expression，and the prognosis of patients with double high expression of miRNA-183 and CA199 was worse than that of patients without double high expression (P<0.05). CONCLUSION：There was a significant increase in the expression of miRNA-183 in serums of the patients with gastric cancer. Moreover，the expression levels of miRNA-183 were related to T stage，TNM stage and histological grading of tumor. Combined detection of serum miRNA-183 and CA199 improved the diagnostic efficiency of gastric cancer and predicted the prognosis of these patients.

Key words: miRNA-183, carbohydrate antigen 199, gastric cancer, tumor markets