Leukaemia

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Laboratory Tests

Full blood count and differential
These are routine tests that are requested to count the number and relative proportion of each of the different types of cells in the blood stream. They give your doctor information about the relative maturity of the blood cells present and they can provide the first evidence that a person has leukaemia. Irregularities in cell counts, such as elevated WBC counts or low red blood cell counts may be due to leukaemia or to a variety of temporary or chronic conditions, but blasts (very immature WBCs) are not normally seen in the blood. If they are present, some kind of leukaemia is likely, and follow-up testing is indicated. The FBC and differential are used to help diagnose leukaemia 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, undifferentiated stem cells, and a mixture of blasts and maturing blood cells. If your doctor suspects leukaemia, they will often request or perform a bone marrow aspiration or biopsy to look directly at the fluid and tissue in the marrow. A 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 leukaemia is present, the type and severity of the disease can be determined.

For more information, see Bone Marrow Aspiration and Biopsy.

Spinal tap (lumbar puncture)
If leukaemia is found in the bone marrow a lumbar puncture may also be done to look for leukaemia cells in the cerebrospinal fluid around the brain and spinal cord.

Cytogenetic analysis and fluorescent in-situ hybridization (FISH)
This is a molecular cytogenetic test used to investigate chromosomal abnormalities associated with leukaemias, other cancers, and genetic disorders. It is used for diagnosis and differentiating the leukaemias: there are translocations such as t(8;21) and many others for acute myeloblastic leukaemia t(15;17) for acute promyelocytic leukaemia and t(9;22) for chronic myeloid leukaemia. These techniques can also detect deletions associated with AML or myelodysplastic syndromes (5q, 7q) and trisomies (trisomy 12) for chronic lymphocytic leukaemia. Karyotyping and/or FISH helps diagnose different leukaemias that may look similar but have different genetic abnormalities and therefore may require different treatment.

Polymerase chain reaction (PCR)
This test amplifies DNA mutations, that are associated with certain leukaemias and may help with determining the prognosis for a certain leukaemia. Classic PCR tests look for for the promyelocytic leukaemia mutation PML-RARA (due to the chromosomal translocation t(15;17)(q22;21)], for the AML1-ETO fusion product (chromosomal translocation t(8;21)(q22;q22)) associated with acute myeloid leukaemia [and for (BCR-ABL (translocation t(9;22)) characteristic of chronic myeloid leukaemia. PCR screening tests look for a large number of known mutations.

Non-Laboratory Tests
Computerized tomography (CT), magnetic resonance imagine (MRI), or positron emission tomography (PET) scans are sometimes used to look for signs of the disease (tumours 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.

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