Full blood count (FBC) 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 your doctor information about the size, shape and relative maturity of the blood cells present. FBCs and differentials are snapshots of what is happening in the body at the time the blood is taken. They are used to detect cell abnormalities, determine their importance, help diagnose their cause, and monitor their course and response to treatment. Irregularities in cell counts, such as elevated WBC counts or low RBC counts, may be due to bone marrow disorders, but they may also be due to a variety of other temporary or chronic conditions.
Bone marrow aspiration/biopsy
If your doctor suspects a bone marrow disorder, he will often order a bone marrow aspiration and biopsy to actually look at the cells and tissue in the marrow.
When a laboratory scientist or doctor examines the sample from your bone marrow under the microscope, the person can see the number, size, and shape of your red and white blood cells and platelet precursors (megakaryocytes), determine the proportions of mature and immature cells, see any overgrowth of fibrous tissue, and detect any cancer cells from cancers that may have spread to the marrow. Most bone marrow disorders can be diagnosed during this examination.
Iron storage can also be estimated by a marrow examination, although if iron deficiency is suspected, other iron tests are usually ordered to confirm the condition and diagnose the cause.
Flow cytometry is a technique that may be used to measure cell surface antigens of cells from the bone marrow, peripheral blood or other body fluids. Antigens are characterized by clusters of differentiation (CD) and each antigen is allocated a number. The technique involves incubating cells in liquid suspension after they have been given a fluorescent tag. An instrument called a flow cytometer is then used to count and examine the cells for normal and abnormal antigens. Numbers of different cell types and abnormalities related to the cell surface antigens are compared with the knowledge of normal samples and helps support different diagnoses. Different disorders can be diagnosed according to a unique pattern of cell type and antigens.
These tests look for several different types of genetic abnormalities in bone marrow cells or circulating white blood cells, including:
- chromosomal translocation; in which part of the chromosome is transferred to different a location, often to a different chromosome. It is associated with chronic myelogenous leukaemia, Burkitt's lymphoma, and many other leukaemias and lymphomas
- single gene changes; these are seen in some lymphomas and haemoglobin disorders.
- clonal populations of white blood cells; where many replicas of a particular WBC are produced. These provide diagnostic evidence for several myelodysplastic syndromes and lymphoid leukaemias.
Techniques involve removing the DNA from a specific cell population in the bone marrow or the blood, manipulating the DNA to find the correct gene, and then using special tests that look for one of the abnormalities listed above in the isolated gene.
Lumbar puncture (spinal tap)
If leukaemia is found in the bone marrow, a lumbar puncture may be performed by the doctor as a follow-up test to look for leukaemic cells in the cerebral spinal fluid.
X-rays and other radiological techniques such as PET (Positron Emission Tomography) or CT (Computed Tomography) scans are sometimes used to look for signs associated with some bone marrow diseases, such as masses of cells in areas like the chest, spleen, and liver.