If a person is suspected to have CLL, some investigations are required to confirm the diagnosis of the disease. Further, these investigations can help in determining the extent of disease and help in selecting an appropriate treatment approach.
Following are some commonly used diagnostic tools for CLL:
Blood tests provide very important information that provides direction to the diagnostic workup of CLL. Following are the commonly employed blood tests for the diagnosis of the CLL:
Complete Blood Cells Count (CBC)
This test provides information on the level of RBCs, WBCs, and platelets. In most cases of CLL, low level of RBCs and platelets and high level of WBCs is observed. A higher level of WBCs is observed due to the presence of monoclonal B-lymphocytes which look like WBCs but cannot perform functions of WBCs.
In this test, a drop of a blood sample is spread on a glass slide and this is observed under a microscope. This test helps in detecting changes in the distribution or appearance of various blood cells. Ruptured lymphocytes or “smudge” cells are usually observed in case of CLL, reflecting the fragility of CLL cells.
In this technique, the blood sample is first treated with some fluorescent antibodies that get attached to certain specific proteins (antigens) on the surface of cells. The treated sample is then analyzed using a laser beam and a detector attached to a computer.
This test can establish the diagnosis of CLL through detection of different types of cells (with specific cell surface proteins) in the blood sample along with the quantification of each type of cells.
Presence of CD19, CD20, CD5, CD23, and CD10 cell surface proteins is usually detected in CLL by this technique. Restricted expression of either kappa or lambda immunoglobulin light chain on the cell surface membrane establishes the clonality of B-cells.
Fluorescent in situ hybridization (FISH)
In this technique, fluorescent RNA probes are used, which bind to a specific portion of a chromosome in the sample cells. Then, the sample can be examined under a microscope to determine the presence of certain chromosomal abnormalities like translocation, addition, or deletion.
This technique is very sensitive, fast, and accurate. This technique is preferably used for detecting common genetic abnormalities in CLL cells, for example, del(13q), del(11q), del(17p), trisomy 12, and mutation in TP53 gene.
Polymerase chain reaction (PCR)
This is a very sensitive diagnostic tool which can detect a very small number of leukemia cells with a specific genetic change, for example, Immunoglobulin heavy-chain variable (IGHV) region gene mutation. This technique is generally used to diagnose minimum residual disease (MRD) in patients after treatment.
Bone Marrow Aspiration/Biopsy
Bone marrow biopsy samples (are not absolutely required) may also be collected and analyzed to obtain information related to certain prognostic factors for CLL. The biopsy sample is then tested in a laboratory and can provide very useful information about the CLL cells such as the pattern of spread (nodular versus interstitial pattern) or the severity of cancerous changes involved, and the presence of specific defective genes or proteins.
In this technique, a very thin portion of a sample is first attached to a microscope glass slide. The sample is then treated with a specific antibody which gets attached to a protein specific to certain types of cancer cells. Some reagents are then added to the treated sample that causes the bound antibody to changes its color. The change in color of the antibody-protein complex can be observed under the microscope, which confirms the type of cancer cells.
The determination of CD38, CD49d, and ZAP-70 expression can be achieved by this technique (or by flow cytometry), which provides prognostic information and guides appropriate treatment selection.
Utility of imaging tests is limited for the diagnosis of Chronic Lymphocytic Leukemia. However, these tests can be used to detect the involvement of different body parts by CLL. Alternatively, these tests are employed to assess accompanying problems like infection.
Computed tomography (CT) scan In this technique, detailed cross-sectional images of body organs are generated using x-rays. It can be utilized for scanning neck, chest, abdomen and pelvis for the diagnosis of any abnormal lymph node or involvement of liver, spleen, or other structures.
Magnetic resonance imaging (MRI) scan This technique provides detailed images of internal body structures using radio waves, strong magnetic field, and gadolinium-based contrast material (which is used via intravenous injection to improve the clarity of the MRI images). It can be utilized for scanning neck, chest, abdomen and pelvis for the diagnosis of any abnormal lymph node or involvement of liver, spleen, or other structures. It is considered very sensitive to detect the involvement of CNS the patients with neurological symptoms.
Differential Diagnosis of CLL
Small lymphocytic lymphoma (SLL)
A disorder closely related to CLL, which is characterized by the presence of malignant monoclonal B-cells mainly in the lymphoid tissue (lymph nodes and spleen) and bone marrow but <5 x 10^9/L malignant cells are present in the blood (as opposed to CLL).
Monoclonal B-cell lymphocytosis (MBL)
A precursor to CLL, which is characterized by the presence of <5 x 10^9/L of abnormal monoclonal B cells in blood but in the absence of palpable lymph node(s), or other clinical features of a lymphoproliferative disorder. About 1% to 2% of patients with MBL progress to CLL, each year.
Prolymphocytic leukemia (PLL)
An aggressive type of lymphocytic leukemia, which is characterized by the presence of an abnormally high number of prolymphocytes, splenomegaly, and minimal involvement of lymph nodes. It can be either B-cell or T-cell type. It tends to grow and spread faster than CLL.
Large granular lymphocyte (LGL) leukemia
A rare T-cell or natural killer (NK)-cell lymphoproliferative disorder, which is characterized by the presence of an abnormally high number of larger than normal lymphocytes in the blood, cytopenia (neutropenia, anemia, and thrombocytopenia), and serological abnormalities (rheumatoid factor, antinuclear antibody, hypergammaglobulinemia, and high beta2- microglobulin). LGL leukemia cells can have features of either T -cells or of (NK)-cells, with NK-cells phenotype tends to be more aggressive.
Hairy cell leukemia (HCL)
A rare chronic B-cell lymphoproliferative disorder, which is characterized by the presence of an abnormally high number of hairy cells (twice as large as normal lymphocytes that have irregular cytoplasmic projections when viewed under the microscope), cytopenia, and splenomegaly. Recently it was found that patients with HCL have mutation in the BRAF (V600E) gene. The HCL tends to progress slowly and have a favorable outcome when treated with the modern therapeutic agents. The HCL represents about 2% of all adult leukemias.