The AUC for serum CEA as a diagnosis of ACA was 0.459 (95% CI: 0.370–0.547, P = 0.358; Fig. 2Ab), and as a diagnosis of CRC was 0.695 (95% CI: 0.627–0.767, P = 0.000; Fig. 2Ad). Here, CEACAM5 is linked to colorectal carcinoma.