Cancer Antigen 125(CA 125) CLIA kit (Chemiluminescence Immunoassay) is an in vitro diagnostic quantitative test kit. CA 125 is found in a high percentage of nonmucinous ovarian tumors of epithelial origin4 and can be detected in serum. This test may be used to monitor certain cancers during and after treatment. In some situations, the test may be used to look for early signs of ovarian cancer in people with a very high risk of the disease.