Tests
Laboratory Tests
Complete blood count and differential
These are routine tests that are ordered to count the number and relative proportion of each of the different types of cells in the blood stream. They give the doctor information about the number and the relative maturity of the blood cells present and they can provide the first evidence if a person has leukemia. Irregularities in cell counts, such as elevated WBC counts or low red blood cell counts may be due to leukemia or to a variety of temporary or chronic conditions, but blasts are not normally seen in the blood. If they are present, some kind of leukemia is likely and follow-up testing is indicated. The CBC and differential are used to help diagnose leukemia and are important tools to monitor the effectiveness of treatment and to detect recurrence.
Bone marrow aspiration/biopsy
Bone marrow exists as a matrix of fibrous supporting tissue, fluid ("liquid marrow"), undifferentiated stem cells, and a mixture of blasts and maturing blood cells. If a doctor suspects leukemia, a bone marrow aspiration and/or biopsy procedure will be carried out to actually look at the fluid and/or tissue ("solid marrow") in the marrow. A pathologist or other specialist then examines the marrow sample (bone and/or fluid) under the microscope, evaluating the number, size, and shape of each of the cell types, as well as the proportions of mature and immature cells. If leukemia is present, the type and severity of the disease can be determined.
Spinal tap (lumbar puncture) and cerebrospinal fluid (CSF) analysis
If leukemia is found in the bone marrow, a spinal tap may also be done to look for leukemia cells in the cerebrospinal fluid. If leukemic cells are seen in the CSF, additional treatment (for example, direct injection of drug into the CSF space) may be necessary.
Immunophenotyping or phenotyping by flow cytometry
This test can be used to help diagnose leukemia and to determine which type of leukemia a person has. Cells from the blood, bone marrow, or lymph nodes are treated with antibodies, which selectively bind to different "CD" and other antigens on the surface or in the cytoplasm of leukemia cells. Flow cytometry then uses a laser beam and computer to detect antibody-bound antigens such as CD3, CD10, CD13, CD15, CD16, CD20, CD33, CD34, CD45, CD56, CD64, TdT, light chains (kappa and lambda). The presence or absence and the intensity of expression of one or more of such antigens help to categorize the type of leukemia present.
Cytogenetics and fluorescent in situ hybridization (FISH)
Cytogenetics (karyotypic analysis, i.e., to detect abnormalities in the number or structure of chromosomes) and molecular cytogenetic analysis by FISH are used to investigate chromosomal abnormalities associated with leukemias, other cancers, and genetic disorders. It is used for diagnosis and differentiating the leukemias: there are translocations for certain acute myeloid leukemias t(8;21) and inv(16)/t(16;16), for acute promyelocytic leukemias t(15;17), and for chronic myelocytic leukemia t(9;22), for acute lymphoblastic leukemias t(12;21), t(9;22) and t(5;14), among others. This technique can also detect deletions associated with AML or myelodysplastic syndromes (5q-, 7q-) and trisomies (trisomy 12) for chronic lymphocytic leukemia. FISH helps diagnose different leukemias that may look similar but have different genetic abnormalities and therefore may require different treatment. For more on this, see the article The Universe of Genetic Testing: Cytogenetics (Chromosome Analysis).
Polymerase chain reaction (PCR)
This test uses DNA that is amplified by PCR to detect DNA mutations, inversions, fusions, or deletions that are associated with certain leukemias and may help with determining the treatment and/or prognosis for a certain leukemia. The better known PCR tests are for:
- acute promyelocytic leukemia [PML-RARA t(15;17)(q22;q12)]
- acute myeloid leukemia [AML1-ETO t(8;21)(q22;q22), and inv(16)(p13;q22)]
- acute B lymphoblastic leukemia [TEL-AML1 t(12;21)(p13;q22)
- myeloid proliferative neoplasm with eosinophilia [FlP1L1-PDGFRA del(4q12)]
- chronic myelogenous leukemia [(BCR-ABL t(9;22)(q34;q11))
There are several other less commonly used PCR tests.
Non-Laboratory Tests
Computerized tomography (CT), magnetic resonance imaging (MRI), or positron emission tomography (PET) scans are sometimes used to look for signs of the disease (tumors and masses of cells) in areas such as the chest. Other imaging scans may also be used to evaluate the status of body organs such as the spleen, liver, and kidney.
For more on these, see the web site RadiologyInfo: The radiology information resource for patients.
