Full-length mRNA transcript sequences for CEA (NM_004363.2) and the CEA splice variant (DKFZp781M2392) were retrieved from the NCBI Reference Sequences database. For the full-length CEA assay we targeted the splice junctions of exons 3 and 4 to design the gene specific probe. For the CEA splice variant assay we targeted the splice junctions of exons 2 and 5 exon to design the gene specific probe. All primer/probes were imported into the Primer Express (Applied Biosystems, Foster City, CA) software tool to ensure the optimal design for utilization in the TaqMan Gene Expression assay procedure. All probes were designed to incorporate a minor groove binding moiety (MGB), and were labeled with a fluorescent dye (FAM) for detection and as a non-fluorescent quencher. Primers and probes were custom ordered from Applied Biosystems. Sequences for all primer/probe combinations are as follows: