What is a CA-125 blood test?

CA 125 (Cancer Antigen 125)

Definition:

CA 125 is a protein (glycoprotein) found on the surface of many cells, including those in the female reproductive system. It is commonly used as a tumor marker, especially for ovarian cancer detection and monitoring.

Full Name:

Cancer Antigen 125 or Carbohydrate Antigen 125

Normal Range:

Normal Value: Less than 35 U/mL

(Values may slightly vary depending on the laboratory.)

Purpose of the Test:

1. Diagnosis Support:

Helps in evaluating women with ovarian masses or symptoms suggestive of ovarian cancer.

2. Monitoring Treatment:

Used to monitor response to treatment in patients already diagnosed with ovarian cancer.

3. Detecting Recurrence:

Helps detect recurrence of ovarian cancer after treatment.

4. Sometimes Used in Other Conditions:

For evaluation of endometriosis, pelvic inflammatory disease, or other cancers when clinically indicated.

Conditions That Can Increase CA 125 Levels:

1. Malignant (Cancerous) Causes:

Ovarian cancer (especially epithelial type)

Endometrial cancer

Fallopian tube cancer

Pancreatic, breast, lung, or gastrointestinal cancers.

2. Benign (Non-cancerous) Causes:

Menstruation

Pregnancy

Endometriosis

Pelvic inflammatory disease (PID)

Liver disease or cirrhosis

Uterine fibroids

Peritonitis or pleuritis

Test Procedure:

A blood sample is drawn from a vein.

The sample is analyzed in the laboratory to measure the level of CA 125 in units per milliliter (U/mL).

Interpretation of Results:

<35 U/mL: Normal range.

> 35 U/mL: May indicate the presence of disease but is not diagnostic of cancer.

Further evaluation, imaging, or biopsy is required to determine the cause.

In known ovarian cancer patients:

Decreasing levels good response to treatment.

Rising levels - possible recurrence or progression.

Limitations:

CA 125 is not specific to ovarian cancer; it can be elevated in many benign conditions.

Not recommended as a screening test for ovarian cancer in the general population.

Most useful in monitoring known cases, not in initial diagnosis alone.

Key Points to Remember:

CA 125 is mainly used to monitor ovarian cancer, not to diagnose it.

Always interpret results alongside clinical findings and imaging studies.

Elevated CA 125 does not always mean cancer, especially in premenopausal women.