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Test ID: CA25 Cancer Antigen 125 (CA 125), Serum

Reporting Name

Cancer Ag 125 (CA 125), S

Useful For

Evaluating patients' response to ovarian cancer therapy


Predicting recurrent ovarian cancer


This test is not useful for cancer detection screening in the normal population.

Clinical Information

Cancer antigen 125 (CA 125) is a glycoprotein antigen normally expressed in tissues derived from coelomic epithelia (ovary, fallopian tube, peritoneum, pleura, pericardium, colon, kidney, stomach).


Serum CA 125 is elevated in approximately 80% of women with advanced epithelial ovarian cancer, but the assay sensitivity is suboptimal in early disease stages. The average reported sensitivities are 50% for stage I and 90% for stage II or greater.


Elevated serum CA 125 levels have been reported in individuals with a variety of nonovarian malignancies including cervical, liver, pancreatic, lung, colon, stomach, biliary tract, uterine, fallopian tube, breast, and endometrial carcinomas.


Elevated serum CA 125 levels have been reported in individuals with a variety of benign conditions including: cirrhosis, hepatitis, endometriosis, first trimester pregnancy, ovarian cysts, and pelvic inflammatory disease. Elevated levels during the menstrual cycle also have been reported.


In monitoring studies, elevations of cancer antigen 125 (CA 125) above the reference interval after debulking surgery and chemotherapy indicate that residual disease is likely (>95% accuracy). However, normal levels do not rule out recurrence.


A persistently rising CA 125 value suggests progressive malignant disease and poor therapeutic response.


Physiologic half-life of CA 125 is approximately 5 days.


In patients with advanced disease who have undergone cytoreductive surgery and are on chemotherapy, a prolonged half-life (>20 days) may be associated with a shortened disease-free survival.

Report Available

1 to 3 days

Day(s) Performed

Monday through Friday

Clinical Reference

1. Sturgeon CM, Duffy MJ, Stenman UH, et al: National Academy of Clinical Biochemistry laboratory medicine practice guidelines for use of tumor markers in testicular, prostate colorectal, breast, and ovarian cancers. Clin Chem. 2008 Dec;54(12):11-79

2. Salani R, Backes FJ, Fung MFK, et al: Posttreatment surveillance and diagnosis of recurrence in women with gynecologic malignancies: Society of Gynecologic Oncologists recommendations. Am J Obstet Gynecol. 2011 Jun;204(6):466-478

3. The Role of the Obstetrician-Gynecologist in the Early Detection of Epithelial Ovarian Cancer. American College of Obstetricians and Gynecologists. 2011. Committee Opinion Number 477

Method Name

Electrochemiluminescent Immunoassay (ECLIA)

Specimen Type


Specimen Required

Patient Preparation: For 12 hours before specimen collection do not take multivitamins or dietary supplements containing biotin (vitamin B7), which is commonly found in hair, skin, and nail supplements and multivitamins.

Collection Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Submission Container/Tube: Plastic vial

Specimen Volume: 1 mL

Collection Instructions: Centrifuge and aliquot serum into plastic vial.

Specimen Minimum Volume

0.75 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Refrigerated (preferred) 5 days
  Frozen  168 days

Reference Values

Males: Not applicable

Females: <46 U/mL

Test Classification

This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
CA25 Cancer Ag 125 (CA 125), S 83082-8


Result ID Test Result Name Result LOINC Value
CA25 Cancer Ag 125 (CA 125), S 83082-8
Mayo Clinic Laboratories | Neurology Catalog Additional Information:

mml-Neuroimmunology, mml-Neuro-oncology, mml-Pediatric