CEACAM5 and neoplasm: To compare the predictive power between mSEPT9 and serum tumor markers during the auxiliary diagnosis of GC, additional McNemer tests and kappa tests were conducted in the GC group, and the results showed that the overall agreement was poor between both tests (kappa ranged from 0.121 to 0.416), and the positive rate of mSEPT9 with the 1/3 algorithm was significantly higher than that of CEA (p = 0.029), CA19-9 (p = 0.007), and CA72-4 (p = 0.012).