This is a test which measures the different types of blood cell and the hemoglobin level. A patient with leukemia is likely to have a low red cell and platelet count and be anemic.
Polycythaemia Vera will cause a very high red cell count and a high packed cell volume (PCV). The PCV is a measure of what proportion of the total blood volume is made up by the red blood cells. Patients with essential thrombocythaemia have very high platelet counts. The white cell count may be normal or reduced.
Peripheral Blood Smear
If the results of a full blood count are abnormal a blood film will be examined under the microscope. The appearance of leukemia and many of the related diseases on a blood film is quite distinctive and the diagnosis is often clear by this stage.
Bone Marrow Biopsy
A bone marrow biopsy is necessary for almost all patients with leukemia or a related disease. The samples are usually obtained from the back of the hip bone, although the sternum (breast bone) may be used instead for bone marrow aspirates. The procedure causes some discomfort but does not take very long. The procedure is usually carried out under local anesthesia.
This may be done on cells from the blood, the bone marrow or both. In leukemia and related diseases there are changes in the chromosomes of the affected cells compared to normal cells from the same patient. The exact pattern of these changes may be important in predicting the likely response to treatment. In some conditions these changes may also allow the use of very sensitive tests to determine whether the disease is responding to treatment.