LoDs in 50 μL serum samples (7 pM or 1.2 ng/mL for CEA, 16 pM or 1.5 ng/mL for NSE, and 6 pM or 0.2 ng/mL for PSA) were below the clinical cut-off levels of all three tumor markers (approximately 5.0 ng/mL CEA, approximately 12.5 ng/mL NSE, and approximately 4.0 ng/mL PSA). Here, CEACAM5 is linked to neoplasm.