Carcinoembryonic antigen antibody (CEA) test
The Carcinoembryonic Antigen (CEA) test is a blood test primarily used to monitor cancer, particularly in patients diagnosed with colorectal and gastrointestinal cancers. CEA is a tumor marker, and the test measures the levels of anti-CEA antibodies that can indicate the presence and extent of cancer. While not recommended for general cancer screening, it can be helpful in staging and planning surgical treatment before operations, as well as detecting cancer recurrence after treatment. The test can also provide prognostic information for other cancers, including lung, liver, breast, ovarian, stomach, and pancreatic cancers.
The CEA test involves a simple blood draw and uses a specific immunoassay procedure to quantify CEA levels. Results must be interpreted carefully, as no standardized reference levels exist; variations can occur based on patient age, condition, and testing methods. Elevated CEA levels may suggest the presence of large or metastatic tumors, while a decrease typically indicates a positive response to treatment. It is important for the results to be assessed in context, as they can be influenced by factors unrelated to cancer. Overall, the CEA test serves as a valuable tool in cancer management, aiding healthcare providers in making informed treatment decisions.
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Carcinoembryonic antigen antibody (CEA) test
ALSO KNOWN AS: Carcinoembryonic antigen antibody test
DEFINITION: Carcinoembryonic antigen antibody (CEA) tests are used primarily to monitor cancer patients to determine whether their disease is recurring and, if so, its stage and extent. CEA is a tumor marker because anti-CEA antibodies bind to epitopes on carcinoembryonic antigens. This allows CEA quantification in body fluids (primarily serum) and CEA detection on cells or tissue sections by immunostaining.
Cancers diagnosed: Primarily colorectal and gastrointestinal cancers, as well as cancers of the rectum, lung, breast, liver, pancreas, stomach, and ovaries.
Why performed: Anti-CEA antibodies are primarily used to diagnose colorectal cancer; they are not recommended for cancer screening, but preoperative determination may assist in staging and surgical treatment planning. After treatment, anti-CEA antibodies may detect recurrence earlier than other techniques. Anti-CEA antibodies are also informative in lung, liver, breast, ovarian, stomach, and pancreatic cancers as they provide prognostic information. Anti-CEA antibodies can also be evaluated in urine (bladder cancer), bronchial lavage fluid (lung cancer), or cerebrospinal fluid (brain tumors) to improve diagnostic accuracy.
A CEA test is needed to check if cancer has spread to other parts of the body. It can also help understand if a particular cancer treatment is effective. CEA tests can also be employed for data to establish a treatment plan.
Patient preparation: No preparation on the part of the patient is necessary.
Steps of the procedure: The procedure involves a simple blood test and consists only of drawing a blood sample from the patient. A typical solid-phase immunoassay protocol is used when anti-CEA antibodies are used to quantitatively determine CEA in body fluids. This involves the addition of the standards and samples to wells or beads with an adsorbed monoclonal anti-CEA antibody to “catch” and immobilize CEA by high-affinity binding to one of CEA’s epitopes. After incubation and washing steps, a second enzyme-conjugated monoclonal anti-CEA antibody against a different CEA epitope is added. CEA in the specimen is “sandwiched” between the two different antibodies and binds the enzyme to the well or bead. After washing, a colorigenic substrate is added. The rate of color development indicates the activity of the antibody-conjugated enzyme, which is used to infer the CEA concentration in the sample by comparison with known standards.
When anti-CEA antibodies are used to visualize CEA in immunostaining procedures semiquantitatively, the cells or tissues are typically fixed and embedded in paraffin, then sectioned onto glass slides for staining and conventional microscopy. Polyclonal anti-CEA antibodies may be chosen for immunostaining to improve sensitivity.
After the procedure: No special care is needed other than keeping the area of the needlestick clean until it is healed to avoid infection.
Risks: A CEA test does not carry any physical risks or side effects, although caution must be exercised in interpreting the results. The CEA test itself poses no risk to the patient. Test results must not be interpreted in isolation to avoid overtreatment or undertreatment.
Results: Standard levels have not been established for CEA tests and vary depending on the patient’s age and condition as well as testing methods. Anti-CEA-based assays of CEA in body fluids are difficult to interpret in isolation; serial measurements are usually inspected for recognizable patterns that indicate response to therapy, lack of response to therapy, or recurrence of disease. Because of heterogeneity among anti-CEA antibodies, the same reagents and methods should be used during longitudinal monitoring. In immunostaining procedures, many anti-CEA antibodies recognize antigens shared by members of the CEA family of glycoproteins, resulting in extensive background staining. In particular, cells from the liver and gallbladder often react with anti-CEA antibodies because they contain biliary glycoprotein. Each test report should include a reference range and be interpreted by the consulting physician.
In general, patients with early-stage, small tumors may have low, even normal, CEA levels. A High CEA reading may indicate the presence of a large tumor that is spreading to othe areas of the body. Later-stage and metastatic disease may yield initially high CEA levels. A subsequent lower CEA level usually indicates reduced tumor activity, whereas a CEA level that rises over time may indicate tumor recurrence.
Bibliography
"CEA Test (Carcinoembryonic Antigen)," Cleveland Clinic, 11 Apr. 2022, my.clevelandclinic.org/health/diagnostics/22744-cea-test-carcinoembryonic-antigen. Accessed 26 June 2024.
Gold, Phil, and Samuel O. Freedman. "Demonstration of Tumor-Specific Antigens in Human Colonic Carcinomata by Immunological Tolerance and Absorption Techniques." Journal of Experimental Medicine, vol. 121, no.3, 1965, pps. 439–62.
Herold, K. E., and Avraham Rasooly. Biosensors and Molecular Technologies for Cancer Diagnostics. Boca Raton, CRC, 2012.
Kankanala, Vijaya L. "Carcinoembryonic Antigen." StatPearls, 23 Jan. 2023, www.ncbi.nlm.nih.gov/books/NBK57817. Accessed 26 June 2024.
Pagana, Kathleen D., and Timothy J. Pagana. Mosby's Manual of Diagnostic and Laboratory Tests. 5th ed. St. Louis, Mosby, 2014.