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 CLL:

Blood tests [2]. A complete blood count (CBC; a routine blood test) is the first test used to begin the process of diagnosing CLL. It is used to measure the number of different types of cells in a sample of a person's blood. A person may have CLL if the blood contains too many white blood cells (called a high white blood cell count). The doctor will also use the blood test to find out which types of white blood cells are increased.

Bone marrow biopsy and aspiration [3]. 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 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 the awareness of pain) may be used.

CLL can usually be diagnosed with blood tests since the cancerous cells are easily found in the blood; a bone marrow biopsy is not needed for most patients. For some patients, it may be used to help determine prognosis (chance of recovery) or provide more information about the reasons that other blood counts may be abnormal. Although a bone marrow biopsy is not often needed to diagnose CLL, it is often done before beginning treatment.

Flow cytometry and cytochemistry. In these tests, cancer cells are treated in the laboratory with chemicals or dyes that provide information about the leukemia and its subtype. CLL cells have distinctive markers (cell surface proteins) on the outside of the cell. The pattern of these markers is called the immunophenotype. These tests are used to distinguish CLL from other kinds of leukemia, which can also involve lymphocytes. Both tests can be done from a blood sample.

Imaging tests. CLL is generally found in many parts of the body, even if the disease has been diagnosed early. Therefore, imaging tests to find out if the cancer has spread are not needed for all patients, although they may sometimes be recommended to find out whether particular symptoms may be related to the CLL and to measure how well treatment is working.

• An x-ray is a way to create a picture of the structures inside of the body, using a small amount of radiation. It may show if cancer is growing in lymph nodes in the chest.
• A computed tomography (CT or CAT) scan [4] (a three-dimensional picture of the inside of the body) can detect lymph nodes with CLL around the heart, windpipe, lungs, and abdomen. Sometimes, a contrast medium (a special dye) is injected into a patient's vein to provide better detail. CT scans can also determine if CLL is in other organs, such as the spleen.

Imaging tests are rarely needed to diagnose CLL, but they are sometimes used before treatment to find all parts of the body that that are affected by the CLL.

Molecular testing: Your doctor may recommend running laboratory tests on the leukemia cells to identify specific genes, proteins, chromosome changes, and other factors unique to the leukemia. Because CLL cells only divide very slowly, looking at the chromosomes often is less useful than using tests to find specific mutations. Fluorescence in situ hybridization (FISH) assays detect a deletion of the long arm of chromosome 13 [del(13q)] in about half of patients. Other common abnormalities include an extra copy of chromosome 12 (trisomy 12), del(11q) or del(17p). Results of these tests can determine how quickly the disease will progress and will help decide whether your treatment options include a type of treatment called targeted therapy (see Treatment [5]).

Learn more about what to expect when having common tests, procedures, and scans [6].

After these diagnostic tests are done, your doctor will review all of the results with you. If the diagnosis is leukemia, these results also help the doctor describe the disease; this is called staging [7]. Learn more about the first steps to take after a diagnosis of cancer [8].