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Home > Patient & Family Resources > Health Library > Cancer Antigen 125 (CA-125) Test
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Cancer antigen 125 (CA-125) is a protein found on the surface of many ovarian cancer cells. It also can be found in other cancers and in small amounts in normal tissue. A CA-125 test measures the amount of this protein in the blood.
CA-125 is used as a tumor marker, which means the test can help show if some types of cancer are present. Most often, the CA-125 test is used to check how well treatment for ovarian cancer is working or to see if ovarian cancer has returned.
The test for cancer antigen 125 (CA-125) may be used to:
Experts do not recommend using the CA-125 test as a screening test for ovarian cancer because it often has false-positive results that can lead to unneeded surgery. But some doctors may recommend the CA-125 test and a transvaginal ultrasound for women who have a very high risk of ovarian cancer, such as those with BRCA gene changes. For these women, the benefits of screening may outweigh the harms.
In general, there's nothing you have to do before this test, unless your doctor tells you to.
When a blood sample is taken, you may feel nothing at all from the needle. Or you might feel a quick sting or pinch.
There is very little chance of having a problem from this test. When a blood sample is taken, a small bruise may form at the site.
Each lab has a different range for what's normal. Your lab report should show the range that your lab uses for each test. The normal range is just a guide. Your doctor will also look at your results based on your age, health, and other factors. A value that isn't in the normal range may still be normal for you.
Current as of:
December 17, 2020
Author: Healthwise StaffMedical Review: Kathleen Romito MD - Family MedicineE. Gregory Thompson MD - Internal MedicineJimmy Ruiz MD - Hematology, Oncology
Current as of: December 17, 2020
Author: Healthwise Staff
Medical Review:Kathleen Romito MD - Family Medicine & E. Gregory Thompson MD - Internal Medicine & Jimmy Ruiz MD - Hematology, Oncology
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