HOW IS ENDOMETRIOSIS DIAGNOSED: CA-125

CA-125 is a substance known as cancer antigen 125 which is produced by the endometrium and is found in the blood. It was discovered while researchers were trying to find a test for ovarian cancer.

Researchers found although it was present in extremely high levels in some women with ovarian cancer, raised levels were also found in some women with a range of gynaecological conditions, including endometriosis, adenomyosis, pelvic inflammatory disease, unexplained infertility and during pregnancy and menstruation. In an attempt to find a reliable blood test for endometriosis researchers have been investigating the levels of CA-125 in women with endometriosis. They have found that the levels in women with minimal and mild endometriosis are no different to those found in women in general but the levels in women with moderate and severe endometriosis are generally significantly higher.

Unfortunately, the CA-12 5 test is not yet sufficiently accurate to replace laparoscopy as a general test for the diagnosis of endometriosis because the levels are not raised in all women with endometriosis and because the levels are raised in a range of conditions other than endometriosis.

It may soon be useful as an aid for the diagnosis of endometriosis and could be used to help decide who needs a laparoscopy For example, if the gynaecologist only vaguely suspects that a woman has endometriosis he may decide to perform a laparoscopy if the CA-125 levels are raised, but not if the levels are normal.

For now, the most useful role of the CA-125 test appears to be in monitoring the progress of the disease after a definite diagnosis has been made. The levels of CA-125 appear to rise as the disease worsens and fall as the disease improves. Therefore, it may be possible to use repeated CA-125 tests to help determine the real effectiveness of drug treatment or to determine whether or not the underlying disease has worsened, improved or recurred, thereby avoiding the need for repeat laparoscopies.

The CA-125 test offers the most promise as a diagnostic test for endometriosis but further work is necessary before it will be accurate and reliable enough to be used by gynaecologists for the diagnosis and monitoring of endometriosis.

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