CA125
QUESTION: What is the ca125 marker?
RESPONSE: CA-125 is a substance shed by cancer cells, also made by inflamed normal cells that line body parts. This substance is shed in body fluids and finds its way into the bloodstream. CA-125II is a new assay that has less variation from day to day. Since the original CA-125 test kits are no longer sold to laboratories, it is believed that few if any old plain CA-125 tests are being given in the United States since Nov. 1996. CA-125 is a test done on a blood sample drawn in a laboratory. A blood sample is drawn, just as for a variety of other laboratory tests. The assay (analysis) assesses the amount of an antibody that recognizes an antigen in tumor cells.
The CA-125-II blood test is best used for observing the trend of an ovarian-cancer patient's results over time, according to one of the test's co-developers.
"The key is that the absolute value of CA-125-II is not very helpful," says Robert C. Bast Jr., M.D. "It's probably not helpful to compare one patient's results with another's."
The results can be:
- True Positive. Approximately 80 percent of women who have ovarian cancer will have an elevated CA-125 in the serum portion of their blood at the time of diagnosis.
- False positive. The rate of "false positives" with CA-125 makes it inadequate for use by itself for screening of high-risk or healthy women. Premenopausal women are more likely than postmenopausal women to receive a "false positive" CA-125. It should be supplemented with transvaginal sonography and a rectovaginal pelvic exam all done at the same time.
- False negative. Again, the rate of "false negatives" also makes it important to use the test as part of a regimen that includes transvaginal sonography and rectovaginal pelvic exam.
- True negative. Women should repeat the test to observe a trend. You will need to ask your doctor to arrange this.
When a CA-125II returns elevated, it can mean any of several benign conditions, or a "false positive" (especially in premenopausal women), or ovarian cancer or another type of cancer.
A physician specifically experienced in the interpretation of CA-125 results can best assess this for the individual patient. Every woman should:
- Have the test repeated several times if there is any doubt about her symptoms or diagnosis or risk factor (family history of ovarian cancer and other factors elevate risk significantly).
Please Note: Approximately 20 percent of women who have ovarian cancer do not ever have elevated CA-125. That is why it is critical to use CA-125 only as part of a diagnostic regiment that includes transvaginal sonography and a rectovaginal pelvic exam.
When having this test, make certain that your health professional and laboratory provide you the following information about your CA-125 test every time you have one done, in writing:
- The generation of the test: CA-125II or CA-125.
- The name of the manufacturer of the test kit.
- The type of assay used.
- Your result
Please Note: Different manufacturers' assays sometimes provide different results. Every lab test produces some errors, or false results. Several companies produce CA-125-II assays (measurement methods); any company could possibly change its assay and its normal range. It is therefore important for each patient to obtain her CA-125-II results in writing, with the normal range stated.
Excerpts from Reuters May 15 What Is the CA-125II Blood Test?
07/20/98
