CA 125

CLINICAL UTILITY:

CA 125 is an antigen normally expressed in embryologic development as part of a glycoprotein. Its role as a tumor marker started with its detection in the sera of a large percentage of ovarian carcinoma patients. This cancer antigen is elevated in approximately 82% of patients with nonmucinous, epithelial ovarian carcinoma. Tissue in which the antigen normally is found include the epithelium of the fallopian tubes, endometrium, endocervix, and the mesothelial surfaces of the pleura, pericardium, and peritoneum. Elevated levels of CA 125 also are associated with neoplasms of the fallopian tubes, endometrium, colon, lung, breast, gastrointestinal tract, and pancreas.

In addition, elevated levels of CA 125 are found in nonmalignant conditions which include acute pancreatitis, peritonitis, pregnancy, various respiratory and digestive tract diseases, and some autoimmune diseases. The highest increases are seen in liver diseases, since the liver may be involved in normal clearance of the CA 125 molecule. Because the levels of CA 125 rise with increased disease, but fall with successful therapy, its measurement has become useful in monitoring therapy. Because of variability, a significant change in CA 125 level is believed to be a 50% or greater rise or fall in serial measurements. Detection of elevated antigen has sometimes preceded clinical or radiological evidence of tumor recurrence, following remission.

METHOD DESCRIPTION:

Measurements of the serum level of CA 125 are made using a solid-phase immunoassay, based on a “sandwich” principle.

REFERENCE RANGE:

<35 Units/ml.

SPECIMEN REQUIREMENTS:

0.5 ml serum. Freeze.