CLINICAL SIGNIFICANCE:
CA125 is a mucin like glycoprotein. It is a surface antigen associated with nonmucinous epithelial ovarian cancer. The protein is sloughed or secreted from the surface of the ovarian cancer cells into the serum or ascites also made by inflamed normal cells that line body parts. This substance is shed in body fluids and finds it's way into the bloodstream. It is a useful tumor marker for evaluating therapy and monitoring disease status in patients under treatment for ovarian cancer.
CLINICAL APPLICATIONS:
1.It is a marker for ovarian and endometrial carcinoma.
2.To monitor for persistent or recurrent serious carcinoma of ovary in post –operative period or during chemotherapy.
3.To monitor therapy in patients with endometriosis.
4.CA 125 is useful in differentiating benign from malignant disease in patients with palpable ovarian masses.
5.Postoperatively the level of CA 125 correlates with the tumor bulk and is a prognostic indicator of clinical outcome.
6.It has been reported that patients with levels>35 U/ml have the highest risk of clinical recurrence .
7.The rate of change in CA 125 is also highly prognostic. A rapid decrease in the level of CA 125 indicates positive response to therapy.
8.Elevated levels after the third course of primary chemotherapy indicate poor outcome.
9.CA 125 is not increased in mucinous adenocarcinoma.
ELEVATED IN:
Malignant diseases:
1.Nonmucinous epithelial ovarian carcinoma.
2.Fallopian tube tumors.
3.Cervical adenocarcinoma.
4.Endometrial adenocarcinoma.
5.Trophoblastic tumors.
6.Squamous cell carcinoma of vulva or cervix.
ACCUARACY OF CA 125 TEST
- The CA 125 test only returns a true positive result for about 50% of stage I ovarian cancer patients.
- The CA 125 test has an 80% chance of returning true positive results from stage II, III, and IV ovarian cancer patients .
LIMITATIONS:
- Before treatment, patients with confirmed ovarian carcinoma frequently have levels of CA 125 within the range observed in healthy individuals.
- Elevated levels can be observed in patients with nonmalignant diseases.
- However several gynaecological disorders can cause a false positive result. Endometriosis, benign ovarian cysts, first trimester of pregnancy, and pelvic inflammatory disease all produce higher levels of CA 125.
- CA 125 test has a lower specificity in premenopausal women than postmenopausal women.
- 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 a part of a diagnostic regime that includes transvaginal sonography and a rectovaginal pelvic exam.
INTERFERENCES:
Heterophilic antibodies in human serum can react with reagent immunoglobulin, interfering with in-vitro immunoassays. Patients routinely exposed to animals or to animal serum products can be prone to this interference and anomalous values may be observed.