CEACAM5 and colorectal carcinoma: It was determined that threshold values of 2.5 μg/l or 5 μg/l produced many false positives (up to 20%), while values of 5 μg/l or 10 μg/l would result in nearly one-third of recurrences being left undiagnosed [6], deeming CEA as an unsatisfactory measure of CRC detection as alluded in other studies [8].