CEACAM5 and colorectal carcinoma: Although serum carcinoembryonic antigen (CEA) does not have sufficient sensitivity or specificity to diagnose CRC (Table 2 PPV: APL, 5.2% (4.6-5.7%); CRC, 0.4% (0.3-0.7%)), it is still considered the most important biomarker for detecting CRC.