cancer antigen CA 125 in serum

Indications

• ovarian cancer
  • screening
  • monitoring of therapy
  • monitoring for recurrence

Reference interval

• normal CA 125 concentration: 0.0 - 35.0 U/mL.

Principle

The ABBOTT CA-125 RIA assay is a simultaneous sandwich, solid- phase, radioimmunoassay. Polystyrene beads coated with mouse monoclonal antibody to CA 125 are incubated with the specimen, standards or controls & tracer. The tracer is composed of I-125 labeled mouse monoclonal antibody. During this incubation, the CA-125 forms 'sandwich' complexes with the monoclonal antibodies. Unbound materials present in the specimen are removed by aspiration of the fluid & washing of the beads. The bound radioactivity is determined by counting the beads in a gamma counter. The bound radioactivity is proportional to the concentration of the CA-125 in the specimen within the working range of the assay. A standard curve is obtained by plotting the CA-125 concentration of the standards vs. bound radioactivity. The CA-125 antigen concentration of unknown & control, run concurrently with the standards, can be determined from the standard curve.

Clinical significance

• CA-125 is a tumor marker of ovarian cancer. 79% of all ovarian cancers are positive for CA-125
• CA-125 levels greater than or equal to 35 units per mL may be found on approximately 1% of healthy individuals & in patients with nonmalignant conditions, such as pericarditis, cirrhosis, severe hepatic necrosis, severe endometriosis, fibroids, first trimester of pregnancy, pelvic inflammatory disease, menstruation & ovarian cysts or in patients with nonovarian malignancies, such as uterine cancer, hepatoma, pancreatic adenocarcinoma, lymphoma, breast cancer & in lung cancer. CA125 tends to be elevated with any inflammatory condition in the abdomen (or thorax ?), both benign & malignant
• CA-125 value below 35 units per mL does not indicate the absence of residual ovarian cancer because patients with histopathologic evidence of ovarian cancer may have CA 125 levels within the range for healthy individuals. Clinical decisions should not be based on a CA 125 value below 35 units per mL.
• It is suggested that the assay not be performed until at least three weeks after the completion of primary chemotherapy & at least two months after abdominal surgery. This is recommended because it is not clear what effect, if any, these procedures may have in the CA-125 value.

Increases

• ovarian cancer
• pericarditis
• cirrhosis
• severe endometriosis
• fibroids
• first trimester of pregnancy
• pelvic inflammatory disease
• menstruation
• ovarian cysts
• nonovarian malignancies
  • uterine cancer
  • hepatoma
  • pancreatic adenocarcinoma
  • lymphoma
  • breast cancer
  • lung cancer

Specimen

• Serum is required to be tested with the ABBOTT CA 125 RIA assay.
• The specimens should be clear & nonhemolyzed whenever possible.
• Serum should fresh, not frozen & thawed repeatedly. When serial samples are to be stored for future tests, aliquoting is suggested to avoid repeated freezing & thawing.
• If assay is performed within 24 hours after collection, the specimen should be stored in the refrigerator at 2-8*C. If the testing will be delayed more than 24 hours, the specimen should be frozen. Mix thoroughly after thawing to ensure consistency in the results. Specimens showing particulate matter, erythrocytes, or turbidity should be centrifuged before testing.

SAMPLE VOLUME: 200 uL of specimen is the minimum volume require

More general terms

• cancer antigen CA 125 in body fluid

Additional terms

• mucin-16 (ovarian carcinoma antigen CA125, ovarian cancer related tumor marker CA125, CA-125, MUC16, CA125)

Component of

• biomarkers for lung cancer screening
• ovarian cancer 5 protein panel
• CA-125/HE4 in serum

Patient information

cancer antigen CA 125 patient information