Bone marrow aspiration and biopsy
At a Glance
Why Get Tested?
To evaluate the type, quantity, and maturity levels of the blood cells present in the marrow; to evaluate the fibrous structure of the marrow; to diagnose or monitor a haematological malignancy; and sometimes to collect a sample of marrow for more specific testing
When to Get Tested?
When a patient is anaemic without an obvious cause and/or has a condition or cancer that may be affecting blood cell production; sometimes when a doctor is investigating a fever of unknown origin, often when the patient is immunocompromised
Sample Required?
A bone marrow sample is normally collected from the hip bone (iliac crest of the pelvis) or sternum
The Test Sample
What is being tested?
There are two methods for sampling bone marrow; an aspirate and a biopsy. The bone marrow, a soft fatty tissue found inside the body’s larger bones, is often described as being like a honeycomb – it is a fibrous network filled with a liquid containing cells in various stages of maturation, and 'raw materials' such as iron, vitamin B12, and folate that are required for cell production. The bone marrow aspirate provides a liquid sample of cells that can be studied individually, and the biopsy collects a cylindrical core that preserves the marrow’s structure and shows the relationships of bone marrow cells to one another and the overall cellularity (relative amount of marrow cells compared to fat).
Red blood cells (RBCs), platelets, and five different types of white blood cells (WBCs) are produced in the marrow as needed, with the number and type of cell being created at any one time based on the use of cells, loss and a continual replacement of old cells. For instance, RBCs, which carry oxygen throughout the body, have a lifespan of about 120 days. The marrow paces RBC production at such a rate as to replace old RBCs that are taken out of circulation and maintain a relatively constant number in the blood. The marrow increases the rate of RBC production whenever the patient's number of RBCs decreases, due to such things as bleeding or haemolysis. The increased rate of production continues until there is a sufficient number of RBCs in the blood stream or until marrow production capacity is reached. If the need approaches this capacity, then an increased number of reticulocytes (immature RBCs) will be released into circulation as the marrow tries to keep up. If the need exceeds capacity then the number of RBCs in the blood stream will decrease and the patient will become increasingly anaemic (symptoms of which include pallor, fatigue, and shortness of breath due to decreased oxygen in the blood).
There are a variety of bone marrow disorders, cancers such as leukaemia, vitamin and mineral deficiencies, inherited conditions and diseases such as aplastic anaemia that can affect the marrow's ability to produce an adequate number of each of the different blood cell types and release them into circulation. These diseases may affect the overall number of cells produced, the proportion of cells produced, and/or the function of the cells. Some bone marrow disorders may lead to a deficiency of one or more cell types while others result in excess production of a specific type or of a specific clone of a cell (a single cell that reproduces without regulation).
Leukaemia, for example, is a cancer of the blood cells. It results in the excessive production of one WBC type at the expense of other cell types and can lead to the release of large quantities of abnormal immature WBCs into the blood stream. These WBCs do not fight infection as other WBCs do and they leave the patient more vulnerable to illness. When leukaemic WBCs crowd out RBC production, the patient becomes anaemic; when they decrease the number of platelets produced, they leave the patient vulnerable to excessive bruising and bleeding. Other conditions, such as vitamin B and folate deficiency or iron deficiency anaemia, lead to the creation of large or small or abnormally shaped RBCs and result in specific types of anaemia. Another disorder, myelofibrosis, is characterised by the overgrowth of the fibrous network found in the marrow, compressing cells and leading to changes in red cell shape and changes in the cell counts.
Bone marrow aspiration and/or biopsy as a 'test' includes both the collection of marrow and bone samples and the evaluation of it under the microscope. A pathologist or haematologist microscopically examines slides containing stained smears of marrow samples (bone and/or fluid). The number, size and shape of each of the cell types present are examined, as are the proportions of mature and immature cells. If leukaemia, or another cancer that has spread to the marrow, is present, it can be diagnosed through this examination and the type and severity of the disease (the stage) can be established.
There are other tests that can also be ordered on the marrow sample, depending on what the doctor requests and what he suspects may be occurring. Additional stains to look for things such as excess iron storage in the marrow, culturing of the marrow to look for viral, bacterial, or fungal infections that may be causing a 'fever of unknown origin' and tests for chromosomal abnormalities are among some of the other analyses the physician may request. In the case of leukaemia, tests to determine the type of leukaemia may be done. These include special stains or determining antigenic markers (immunophenotype) to show just what type of leukaemia is present. Testing the bone marrow cells for specific molecular mutations can be used for diagnosis of many haematological malignancies.
How is the sample collected for testing?
The bone marrow aspiration and/or biopsy procedure is performed by a doctor or other trained specialist. Both types of samples may be collected from the hip bone (pelvis) and marrow aspirations may be collected from the sternum (breastbone). In children, samples may also be collected from a vertebrae in the back or from the femur (thigh bone).
The most common collection site is the iliac crest (top ridge) of the hip bone. Before the procedure the patient's blood pressure, heart rate and temperature are measured and evaluated to make sure that they are within normal limits and some patients are given a mild sedative. The patient is then asked to lie down on his or her stomach or side for the collection and their lower body is draped with cloths so that only the area surrounding the site is exposed.
The site is cleaned with an antiseptic such as iodine and injected with a local anaesthetic. When the site has numbed the doctor inserts a needle through the skin and into the bone. For an aspiration, the doctor attaches a syringe to the needle and pulls back on the plunger. This creates vacuum pressure and pulls a small amount of marrow into the syringe. For a bone marrow biopsy, the doctor uses a special needle that allows the collection of a core (a cylindrical sample) of bone and marrow.
Even though the patient's skin has been numbed, the patient may feel brief but uncomfortable pressure (pulling and/or pushing) sensations during these procedures. After the needle has been withdrawn a sterile bandage is placed over the site and pressure is applied. The patient is then usually instructed to lie quietly until his or her blood pressure, heart rate and temperature are normal, and then to keep the collection site dry and covered for about 48 hours.
The Test
How is it used?
The bone marrow biopsy and aspiration provide information about the status of and capability for blood cell production. They are not routinely ordered and in fact the majority of people will never have one done. A marrow aspiration and/or biopsy may be ordered to help evaluate blood cell production, to help diagnose leukaemia, to help diagnose a bone marrow disorder, to help diagnose and stage a variety of other types of cancer (to determine spread into the marrow), and to help determine whether a severe anaemia is due to decreased RBC production, increased loss, abnormal RBC production and/or to a vitamin or mineral deficiency or excess. Conditions that affect the marrow can affect the number, mixture and maturity of the cells and can affect its fibrous structure.
A bone marrow sample may also be evaluated and cultured for the presence of microorganisms such as fungi, bacteria, or mycobacteria (such as that which causes tuberculosis) when the patient has a fever of unknown origin. Additional marrow testing may be ordered when it is suspected that the patient has a chromosomal abnormality and/or a disorder associated with iron storage that may cause iron to accumulate in the marrow.
When a person is being treated for a cancer, a bone marrow aspiration and/or biopsy may be ordered to evaluate the response to therapy to determine whether suppressed marrow function is beginning to return to normal.
A FBC and reticulocyte count are frequently ordered along with the bone marrow aspiration/biopsy. The results are used to help evaluate cell production in the marrow and compare it to current cell populations in circulation.
When is it requested?
A bone marrow aspiration and/or biopsy may be indicated as follows:
As a diagnostic procedure when one of the following is suspected:
- Aplastic anaemia
- Acute leukaemia
- Myelodysplastic syndrome
- Chronic myelogenous leukaemia
- Myelofibrosis and essential thrombocythaemia
- Multiple myeloma
- Severe thrombocytopenia and/or anaemia and/or neutropenia
As a staging procedure in:
- Hodgkin's and Non-Hodgkins lymphomas
- Small cell carcinoma of the lung (although this not frequently done anymore)
For culturing:
- when fever is present in HIV/AIDS or other immunocompromised patient
- in patients suspected of having Brucellosis or Typhoid fever
A bone marrow biopsy and aspiration may also be ordered at intervals when a person is being treated for a cancer to evaluate whether marrow function is being suppressed and if it is, when its function begins to recover.
What does the test result mean?
With a bone marrow biopsy and aspiration the doctor is evaluating what is in the marrow in order to determine whether the cells found are normal and present in typical quantities, to determine whether there are cells present that shouldn't be there (such as abnormal cells that are characteristic of specific cancers or disorders such as the Gaucher cell found with Gaucher's disease or the foamy lipid-filled Niemann-Pick cell found with Niemann-Pick disease), and to determine what is missing.
The training and expertise of the pathologist or haematologist evaluating the marrow samples allows them to sort through the marrow clues and tell the doctor what is happening in the marrow. In most cases, this information can confirm or rule out a diagnosis and bone marrow involvement, but it can also point out the need for further investigation. For instance, if there are a decreased number of RBCs in the blood and an increased number of reticulocytes, and a marrow evaluation shows that RBC production appears normal but increased, then the doctor knows that marrow production of RBCs has increased appropriately to meet a RBC demand. What s/he still doesn't know is the reason for the demand. It could be due to an acute or chronic loss of RBCs (such as may occur with gastrointestinal bleeding) or due to acute or chronic RBC destruction (such as sometimes occurs with an artificial heart valve).
A patient with few RBCs and no increase in reticulocytes may have aplastic anemia (suppressed RBC production in the marrow). An evaluation of the bone marrow may confirm this condition but it does not necessarily tell the doctor whether it is due to a bone marrow disorder, radiation, exposure to certain chemicals, some cancers, cancer treatment or due to a tuberculosis infection.
The doctor takes the information that s/he receives from the marrow evaluation and combines it with information from a clinical examination, blood tests and a variety of other tests, such as imaging scans and X-rays, to reach a final diagnosis. It can be a straightforward process or it can be a complex diagnostic puzzle. Patients should stay involved in this process by talking to their doctor before and after a bone marrow biopsy and/or aspiration, asking what her/his suspicions are, what kind of information s/he is hoping to obtain from the evaluation, and what follow-up tests might be indicated.
Is there anything else I should know?
Complications from the bone marrow aspiration and/or biopsy procedure are rare, but some patients may have excessive bleeding at the collection site or develop an infection. Patients should tell the doctor about any allergies they have, and about any medications or supplements they are taking prior to the procedure and should contact their doctor promptly if they experience persistent or spreading redness or bleeding at the site, a fever or increasing pain.
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