Cancer Antigen 27.29 (CA 27-29)
CA 27-29 is a protein that can appear in the blood at higher levels in connection with certain breast tissue conditions, and the test measures how much is present. It is used mainly to help monitor a condition that has already been diagnosed.
CA 27-29 is not a screening or diagnostic test on its own, and it is most useful for tracking trends over time in someone with a known diagnosis. It is closely related to CA 15-3 and shares many of the same limitations. A single reading carries little meaning without your broader clinical context.
A raised CA 27-29 is not a diagnosis and can result from several benign causes, including liver disease, benign breast conditions, and other inflammatory states. Values can also vary from test to test for reasons unrelated to any serious condition. Your clinician therefore emphasizes the trend across repeated measurements rather than any single value.
A low or normal CA 27-29 is the common, expected finding in most healthy people and is generally reassuring. In someone under monitoring, a stable low level is typically viewed favorably.
There is no universal target, and reference ranges differ between laboratories, so the result should not be self-interpreted. A clinician should review CA 27-29 alongside your history and prior values to determine what it means for you.
Sources
Educational context only, not medical advice or a diagnosis. Reference ranges vary by lab, age and sex; always discuss your results with a clinician.