Doctors use many tests to diagnose cancer and find out more about the disease. Some tests may also determine which treatments may be the most effective. For most types of cancer, a biopsy is the only way to make a definitive diagnosis of cancer. If a biopsy is not possible, the doctor may suggest other tests that will help make a diagnosis. Imaging tests may also be used. Your doctor may consider these factors when choosing a diagnostic test:

• Age and medical condition
• Type of cancer suspected
• Severity of symptoms
• Previous test results

The following tests may be used to diagnose or monitor CML:

Blood tests [2]. Many people are diagnosed with CML before they have any symptoms through a blood test, called a complete blood count (CBC). A CBC counts the number of different kinds of cells in the blood. A CBC is often done as part of a regular physical examination. People with CML have high levels of white blood cells. When the CML is more advanced, there may also be low levels of red blood cells (called anemia [3]) and either elevated or decreased numbers of platelets.

Bone marrow biopsy and aspiration [4]. These two procedures are similar and often done at the same time. Bone marrow has both a solid and a liquid part. A bone marrow biopsy is the removal of a small amount of solid tissue using a needle. An aspiration removes a sample of fluid with a needle. The sample(s) are then analyzed by a pathologist (a doctor who specializes in interpreting laboratory tests and evaluating cells, tissues, and organs to diagnose disease). A cytogenetic analysis (see below) may also be done on the marrow samples. A common site for a bone marrow biopsy and aspiration is the pelvic bone, which is located in the lower back by the hip. The skin in that area is usually numbed with medication beforehand, and other types of anesthesia (medication to block awareness of pain) may be used.

Molecular testing. Your doctor may recommend running laboratory tests on the leukemia cells to identify specific genes, proteins, and other factors unique to the leukemia. Results of these tests will help decide whether your treatment options include a type of treatment called targeted therapy (see Treatment [5]).

Cytogenetics is the analysis of a cell's chromosomes, including the number, size, shape, and arrangement of the chromosomes. This test can sometimes be done on the peripheral (circulating) blood when the CML is first diagnosed, but it requires immature blood cells that are actively dividing. Because of this, a bone marrow sample (see above) is usually best. After treatment begins, cytogenetic testing is repeated on another bone marrow sample to find out if there are fewer cells with the Philadelphia chromosome. All people with CML have the Philadelphia chromosome or the BCR-ABL fusion gene (described in the Overview [6] section), so they are used to confirm the diagnosis. For a small number of patients, increased blood cell counts may suggest CML, but the patients do not have the Philadelphia chromosome or the BCR-ABL fusion gene; therefore, they do not have CML but instead have a different type of chronic myeloproliferative disease (a disease in which there are too many red blood cells, white blood cells, or platelets). Treatment of this disease is different from that of CML.

Cytogenetic testing for CML is used to monitor how well treatment is working and if it is reducing the number of cells with the Philadelphia chromosome. The following tests are sometimes used with cytogenetic testing:

• Fluorescent in situ hybridization (FISH) is a test used to detect the BCR-ABL gene and to monitor the disease during treatment. This test does not require dividing cells and is done using a blood sample or bone marrow cells. This test is a more sensitive way to find CML than the standard cytogenetic tests that identify the Philadelphia chromosome.

• Polymerase chain reaction (PCR) is a DNA test that can find the BCR-ABL fusion gene and other molecular abnormalities. PCR tests may also be used to monitor how well treatment is working. This test is quite sensitive and, depending on the technique used, can find one abnormal cell mixed in with approximately 1 million normal cells. This test also uses a blood sample or bone marrow cells.

Imaging tests. Doctors may use imaging tests to determine if the cancer is affecting other parts of the body. For example, a computed tomography (CT or CAT) scan [7] or ultrasound [8] examination is sometimes used to look at the size of the spleen in patients with CML. A CT scan creates a three-dimensional picture of the inside of the body with an x-ray machine. Sometimes, a contrast medium (a special dye) is injected into a patient's vein to provide better detail. An ultrasound is a test that uses high-frequency sound waves to produce images of the inside of the body.

Find more about what to expect when having common tests, procedures, and scans [9].

After these diagnostic tests are done, your doctor will review all of the results with you. If the diagnosis is CML, these results also help the doctor describe the phase [10] of the disease. Learn more about the first steps to take after a diagnosis of cancer [11].