Why am I asked to undergo a CA 125 blood test?
Q: My left ovary is bigger than the right ovary. My doctor has told me to undergo CA-125 blood test. Is it something serious?
A:In general, post-menarchal ovaries measure 2.5-5 cm in length, and 1.5 to 3 cm. in width and depth. As the ovary has a variable, usually oval shape, size is best expressed as an estimated volume. The normal volume is Pre-pubertal 0 - 8 ml; Post-pubertal 0-18 ml; Post-menopausal 0-8 ml. Between the ages of 20 and 50 years, the volume ranges from 2.5-23 ml. The ratio of larger to smaller ovary should normally be less then 2:1. CA 125 (cancer antigen 125) is a protein whose levels are increased in most patients with Stage 3 and 4 ovarian cancer while only about half the patients show raised levels in early stage. It can also be elevated in many non-cancerous diseases of the reproductive tract like endometriosis, pelvic Inflammatory disease, uterine fibroids & adenomyosis, ectopic pregnancy and benign ovarian tumours. As the test gives too many false positives and is not raised in the early stages of the disease, it cannot be used as a tool for screening. The rate at which CA-125 levels increase is a more accurate method of detecting the presence of ovarian cancer, than a single CA-125 test. A level of greater than 35 U/ml is generally accepted as being increased.