What Other Tests are Used to Diagnose Blood Cancer?
In addition to blood tests and bone marrow aspiration, there are several tests that are commonly run to analyze the blood and bone marrow cells during the diagnostic process of different blood cancers.
Morphology is the study of the physical appearance or structure of an organism, including cells. Cancerous cells appear distinctly different than normal, healthy cells under the microscope. To make a diagnosis of blood cancer, a morphologic assessment is done to identify if there are cancerous cells in the blood. Morphologic assessment may be done with a peripheral blood smear, in which a drop of blood is examined under the microscope to count and note the structure of the blood cells, including red blood cells (RBCs), white blood cells (WBCs), and platelets, as well as any abnormalities that may be present.1
Immunophenotyping is a process of identifying cells based on the types of antigens or markers on their surface. It is typically done to diagnose leukemias and lymphomas.1,2
Two tests utilized for immunophenotyping are flow cytometry and immunohistochemistry. Flow cytometry is a technology that uses a laser to measure multiple characteristics of cells. Immunohistochemistry uses a microscope. In both these tests, the blood or bone marrow sample is stained with a dye. Certain dyes cause a color change in blood cancer cells by attaching to the antigens present, which normal cells do not have. This allows doctors to identify any cancer cells.1-3
Cytogenetic testing, also called karyotyping, determines any potential chromosomal abnormalities or mutations in a blood cancer. These tests are helpful in diagnosis, prognosis, selecting appropriate treatment, and monitoring treatment effectiveness. In conventional cytogenetic testing, the cells are grown in the laboratory to detect changes to chromosomes that are visible during cell division.3
Two additional types of genetic tests are fluorescent in situ hybridization (FISH) and polymerase chain reaction (PCR). FISH uses a special fluorescent dye that only attaches to specific genes or chromosomal abnormalities in blood or bone marrow samples, and help make them detectable. While the test results can be helpful in identifying known chromosomal changes, like the Philadelphia chromosome in acute lymphocytic leukemia, FISH does not look at overall chromosomal mutations.3,4
PCR is a sensitive DNA test that can detect specific genetic changes in cancer cells. Like FISH, it does not look at overall chromosomal changes but can be helpful in detecting certain genetic mutations. PCR may be used after treatment to determine if any cancer cells with a specific mutation are still in the blood or bone marrow.3
HLA testing (also called histocompatibility testing or HLA typing) measures the human leukocyte antigens on an individual's cells. In some types of blood cancer, bone marrow transplants may be used as a treatment. HLA testing is critical for bone marrow transplants to closely match the HLA antigens between the recipient and donor.1 HLA testing is done to match organ and tissue transplant recipients with compatible donors to reduce the risk of rejection of the transplant. The HLA antigens (proteins) present on the surface of the cells help the body's immune system identify which cells are "self" and which are "foreign." Foreign cells can trigger an immune response.1