A type of Pap test. A Pap test is a procedure in which cells are scraped from the cervix for examination under a microscope. It is used to detect cancer or changes that may lead to cancer. A Pap test can also show conditions that are not cancer, such as infection or inflammation. In a liquid-based Pap test, the cells are rinsed into a small container of liquid. The cells are then placed onto slides by a special machine and examined under a microscope to see if the cells are abnormal.