CD-123 test is used to measure the level of CD 123 antibodies in the blood. The test is required to confirmed myeloid leukemia and is useful during the treatment of leukemia. The test is also necessary during the treatment as well as after the treatment of Myeloid Leukaemia. Myeloid Leukaemia is a type of cancer that starts in the blood-forming cells of the bone marrow. The disease is characterized by the rapid abnormal growth of white blood cells that build up the bone marrow and hence interfere with the production of normal blood cells.