Diagnosing chronic lymphocytic leukemia (CLL) usually involves a simple blood test. However, your doctor may want to also perform a bone marrow test before treatment to establish a baseline to measure your treatment response against.
After your doctor or clinician takes your blood, he or she sends it to a lab for a complete blood count (CBC), which shows the number of red cells, white cells and platelets in your blood. If you have CLL, you may have lower-than-normal levels of red cells and platelets. Your white cell count will be higher than normal.
Bone Marrow Tests
You usually don't need a bone marrow test for a CLL diagnosis to be confirmed. Instead, your doctor or oncologist (cancer specialist) may want to examine your bone marrow to establish a baseline. The goal of baseline testing is to gather certain information about your blood to compare with new results taken during treatment to measure your response to therapy.
Bone marrow testing involves two steps usually done at the same time in a doctor's office or a hospital:
- A bone marrow aspiration to remove a liquid marrow sample
- A bone marrow biopsy to remove a small amount of bone filled with marrow
Your doctor will examine your bone marrow to look at how your cells are grouped and classify them into one of four kinds of CLL cell patterns:
Your baseline test will establish:
- An increase in the number of lymphocytes in your marrow
- Often a decrease in the number of normal marrow cells
If your blood cell counts remain low during treatment, repeated bone marrow tests can help your doctor determine whether the disease or its treatment are causing the low counts.
Additional Lab Tests
After taking your blood and bone marrow samples, your doctor works with a hematopathologist to confirm a diagnosis, identify the chronic lymphocytic leukemia (CLL) stage and look for certain changes in your chromosomes. A hematopathologist is a specialist who studies blood cell diseases by looking at samples of blood and marrow cells and other tissues.
The hematopathologist uses one or more lab tests such as those below to examine your blood cells:
- Immunophenotyping looks for antigens on the surfaces of lymphocytes to determine whether they originated from a single cancer cell (monoclonal) and whether the CLL came from a B cell or a T cell. Flow cytometry is one type of test used for immunophenotyping.
- An immunoglobulin test is used to check the immunoglobulin level in your blood. Immunoglobulins, also called gamma globulins, are proteins called “antibodies” in the blood that fight infection. CLL cells do not make effective antibodies. CLL cells also interfere with the ability of the remaining normal lymphocytes to make antibodies. As a result, people with CLL often have low levels of immunoglobulins, which increases their risk of getting infections. If that's the case, your doctor may give you immunoglobulin injections.
- Fluorescence in situ hybridization (FISH) is a special test for studying chromosomes in tissue using DNA probes tagged with fluorescent molecules that emit light of different wavelengths (and different colours). FISH can be helpful in assessing risk and treatment needs, and for monitoring treatment effectiveness, by providing a sensitive test to see abnormal cells, such as cells with deletions of 17p.
- G-banding karyotyping examines your chromosomes' arrangement, size, shape and number using a special dye called Giemsa to get a better look at the banding patterns of chromosome pairs.
Common Chromosome Changes
Common chromosomal abnormalities that affect CLL cells include:
- A deletion (loss) on the long arm of chromosome 13 (13q-). This is the most common chromosome change found in CLL. If no other abnormal chromosome changes are present, this type of CLL has a relatively favorable outcome (prognosis).
- An extra copy of chromosome 12 (trisomy 12). Trisomy 12 occurs in about 10 percent to 20 percent of CLL patients. It's associated with intermediate-risk CLL and is high risk if other abnormal chromosome changes are present.
- A deletion on the short arm of chromosome 11 (11q-). This appears in up to 20 percent of CLL patients. These patients tend to be younger than the average CLL patient, and the disease is considered high risk.
- Structural abnormalities in chromosome 14 or chromosome 6. This indicates higher-risk disease.
- A deletion on the short arm of chromosome 17 (17p-). A critical gene called TP53 is typically deleted. People with (17p-) tend to have higher-risk disease and usually don't respond well to standard initial therapy. Their CLL treatment needs to be approached in a different manner.