CA 27-29 test
The CA 27-29 test, also known as Carbohydrate Antigen 27-29, is a blood test used primarily as a tumor marker, particularly for monitoring breast cancer patients who have been treated for Stage II and Stage III cancers. It measures levels of a transmembrane glycoprotein that may indicate the presence of various cancers, including breast, ovarian, colon, and others. Although CA 27-29 is not specific enough for cancer screening, elevated levels can suggest tumor burden, meaning higher levels may correlate with larger tumors. The test is performed through a simple blood draw, with no special preparation required from the patient. While the procedure carries minimal risks such as slight bleeding or infection, these are generally considered manageable. Results are interpreted based on reference intervals, typically indicating normal levels at 0–32 units per milliliter (U/mL), with elevated levels being over 32 U/mL. CA 27-29 levels may also be influenced by non-cancerous conditions, such as pregnancy and certain diseases, making it essential for healthcare professionals to interpret results within a broader clinical context.
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CA 27-29 test
ALSO KNOWN AS: Carbohydrate antigen 27-29, cancer antigen 27-29
DEFINITION: Similar to CA 15-3, CA 27-29 is a transmembrane glycoprotein (carbohydrate-containing protein, or mucin) found in several tissue types. This class of glycoproteins is thought to play a role in reducing cell-to-cell interaction and the inhibition of tumor cell cytolysis. The core protein component is identical; the carbohydrate concentration (degree of glycosylation) is the component differentiating between tissue types. Serum/plasma levels are determined by immunoassay.
Cancers diagnosed: CA 27-29 is not an organ-specific marker and has been found at elevated levels in breast, ovarian, colon, stomach, kidney, lung, pancreatic, uterine, and liver cancers. Additionally, increased CA 27-29 levels can be found concomitant with conditions such as first trimester pregnancy, endometriosis, ovarian cysts, and breast, kidney, and liver disease.
Why performed: Because CA 27-29 is not sensitive or specific enough to be used as a screening test, its primary utility is as a tumor marker for monitoring response to therapy and recurrence in previously treated Stage II and Stage III breast cancer patients. Blood levels are typically proportional to the tumor burden (mass), with higher levels of CA 27-29 indicative of the presence of a larger tumor. Physicians will typically order either CA 27-29 levels or CA 15-3 levels but not both as they are considered essentially equivalent in diagnostic value.
Patient preparation: No special patient preparation is required for accurate CA 27-29 analysis.
Steps of the procedure: A blood sample is collected, typically by venipuncture. The collected serum (or plasma) is tested by immunoassay, which involves capturing CA 27-29 present in the sample by means of monoclonal anti–CA 27-29 antibodies. A second, detection (labeled) antibody is then introduced, which subsequently binds to the CA 27-29/anti-CA 27-29 complex. The addition of a substrate results in a detectable signal, the level of which is directly proportional to the amount of the CA 27-29 present in the sample.
After the procedure: Pressure should be applied to the venipuncture site in order to avoid the development of a hematoma.
Risks: The risks of venipuncture are slight but include excessive bleeding, fainting, hematoma, and infection (always a slight risk any time the skin is broken).
Results: Although each laboratory establishes reference intervals based on the local, normal population, a basic interpretive guideline for CA 27-29 places normal at 0–32 units per milliliter (U/mL) and elevated at more than 32 U/mL. In 2013, the American Cancer Society stated that the normal level of CA 27-29 is usually less than 40 U/mL, depending on the testing laboratory.
Bibliography
“CA 27-29 - Health Encyclopedia.” University of Rochester Medical Center, www.urmc.rochester.edu/encyclopedia/content.aspx?contenttypeid=167&contentid=ca‗27‗29. Accessed 18 June 2024.
Amer. Cancer Soc. Tumor Markers. N.p.: ACS, 30 Oct. 2013. Digital file.
Amer. Cancer Soc. "Tumor Markers Found in Blood or Urine" Cancer.org. ACS, 30 Oct. 2013. Web. 16 Sept. 2014.
Amer. Soc. of Clinical Oncology. "Tumor Markers for Breast Cancer." Cancer.Net. ASCO, 2005–14. Web. 16 Sept. 2014.
Berger, Barbara J. Laboratory Tests and Diagnostic Procedures. 6th ed. St. Louis: Elsevier, 2013. Digital file.
Tobias, Jeffrey S., Daniel Hochhauser, and Robert L. Souhami. Cancer and Its Management. 6th ed. Chichester: Wiley, 2010. Digital file.