From an article by David Johnson, Ph.D., and David Sandmire, M.D. with Daniel Klein
The carcinogenic antigen (CA) 125 blood test measures levels of a protein that is normally confined within a cell. Ovarian cancer cells may produce an excess of these protein molecules, and therefore the CA-125 test can help in diagnosing and monitoring this disease. It’s important to remember that simply measuring blood levels of CA-125 alone cannot effectively find early ovarian cancer. In many early-stage ovarian cancers, this molecule is not necessarily released in large amounts. In conjunction with a transvaginal ultrasound (TVU) screening, however, the CA-125 test can be very effective. A transvaginal ultrasound, also known as an endovaginal ultrasound, involves the use of sound waves to delineate internal structures. The transducer produces images that can be seen on a video monitor, and a hard copy can be made on film.