DESCRIPTION

CEACAM5, also known as carcinoembryonic antigen (CEA) or CD66e, is a member of the immunoglobulin superfamily, mainly serving as a cell adhesion molecule mediating intercellular contact by both homophilic and heterophilic binding. CEACAM5 is overexpressed in a wide variety of human cancers, including colon, breast, and lung. It inhibits anoikis and plays a role in tumorigenesis and metastasis. CEACAM5 is not usually present in the blood of healthy adults. However, it has been found that serum from people with colorectal, gastric, pancreatic, lung, and breast carcinoma has higher levels of CEACAM5 than healthy people. CEACAM5 is a tumor marker and is routinely exploited for diagnosis.

PRINCIPLE OF THE ASSAY

An anti-tag antibody is pre-coated onto the bottom of wells. After adding antigen or samples, Tagged-Capture antibody and HRP-conjugated detection antibody, a sandwich complex is formed in the solution. TMB acts as a HRP substrate, and the solution color will change from colorless to blue. A stop solution containing sulfuric acid turns the solution yellow. The color intensity is proportional to the quantity of bound protein, which is measurable at 450 nm with the correction wavelength set at 630 nm.

PRECISION

Intra-assay Precision (Precision within an assay) Three samples of known concentration were tested 8 times on one plate to assess intra-assay precision. Inter-assay Precision (Precision between assays) Three samples of known concentration were tested in 16 separate assays to assess inter-assay precision.

Intra-assay Precision

Sample	n	Mean (pg/mL)	SD	CV%
1	8	474.2	13.4	2.8
2	8	109.9	2.6	2.4
3	8	55.7	1.7	3.1

Inter-assay Precision

Sample	n	Mean (pg/mL)	SD	CV%
1	16	474.5	11.2	2.4
2	16	109.7	2.6	2.4
3	16	54.0	2.5	4.6

RECOVERY

The recovery of human CEA/CEACAM5 spiked to three different levels throughout the range of the assay in various matrices was evaluated.

Sample Type		Average% of Expected	Range (%)
Human plasma	1:8	114	112-117
	1:16	109	103-115
Saliva	1:40	96	91-99
	1:80	93	90-96

LINEARITY

To assess the linearity of the assay, samples were diluted with the appropriate Sample Diluent to produce samples with values within the dynamic range of the assay. (The saliva was initially diluted 1:5.)

		Human plasma	Saliva
1:2	Average% of Expected	100	100
	Range (%)	-	-
1:4	Average% of Expected	99	104
	Range (%)	89-109	96-111
1:8	Average% of Expected	84	96
	Range (%)	82-86	87-104
1:16	Average% of Expected	76	107
	Range (%)	75-76	97-117

CALIBRATION

This immunoassay is calibrated against a highly purified recombinant human Human CEA/CEACAM5 One-Step ELISA Kit produced at Sunlong Medical™.