Bone marrow examination
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'''Bone marrow examination''' refers to the [[pathology|pathologic]] analysis of samples of [[bone marrow]] obtained by '''bone marrow biopsy''' (often called a [[trephine]] biopsy) and '''bone marrow aspiration'''. Bone marrow examination is used in the diagnosis of a number of conditions, including [[leukemia]], [[multiple myeloma]], [[anemia]], and [[pancytopenia]]. The bone marrow produces the cellular elements of the [[blood]], including [[platelet]]s, [[red blood cell]]s and [[white blood cell]]s. While much information can be gleaned by testing the blood itself (drawn from a vein by [[phlebotomy]]), it is sometimes necessary to examine the source of the blood cells in the bone marrow to obtain more information on [[hematopoiesis]]; this is the role of bone marrow aspiration and biopsy.
[[Image:acute_leukemia-ALL.jpg|thumb|right|A [[Wright's stain]]ed bone marrow aspirate smear from a patient with leukemia.]]
==Components of the procedure==
Bone marrow samples can be obtained by '''aspiration''' and '''trephine biopsy'''. Sometimes, a bone marrow examination will include both an aspirate and a biopsy. The aspirate yields semi-liquid bone marrow, which can be examined by a [[pathologist]] under a [[light microscope]] as well as analyzed by [[flow cytometry]], [[cytogenetics|chromosome analysis]], or [[polymerase chain reaction]] (PCR). Frequently, a trephine biopsy is also obtained, which yields a narrow, cylindrically shaped solid piece of bone marrow, 2mm wide and 2cm long, which is examined microscopically (sometimes with the aid of [[immunohistochemistry]]) for cellularity and infiltrative processes.
{|class="wikitable"
|+ Comparison
|-
! !! Aspiration !! Biopsy
|-
! Advantages
|
*Fast
*Gives relative quantity of different cell types
*Gives material to further study, e.g. [[molecular genetics]] and [[flow cytometry]]
||
*Gives cell and [[bone marrow stroma|stroma]] constitution
*Represents all cells
*Explains cause of "dry tap" (aspiration gives no blood cells)
|-
!Drawbacks
| Doesn't represent all cells || Slow processing
|-
|}
Aspiration doesn't always represent all cells since e.g. [[lymphoma]] stick to the [[Cancellous bone|trabecula]], and would thus be missed by a simple aspiration.
==Site of procedure==
Bone marrow aspiration and trephine biopsy are usually performed on the back of the hipbone, or posterior [[iliac crest]]. However, an ''aspirate'' can also be obtained from the [[sternum]] (breastbone). A ''trephine biopsy'' should never be performed on the sternum, however, due to the risk of injury to [[blood vessel]]s, [[lung]]s or the [[heart]].
==How the test is performed==
[[Image:Bone_marrow_biopsy_needle.jpg|thumb|right|150px|A needle used for bone marrow aspiration, with removable stylet.]]
A bone marrow biopsy may be done in a health care provider's office or in a hospital. [[Informed consent]] for the procedure is typically required. The patient is asked to lie on his or her abdomen ([[prone]] position) or on his/her side (lateral [[decubitus]] position). The skin is cleansed, and a local [[anesthetic]] such as [[lidocaine]] is injected to numb the area. Patients may also be pretreated with [[analgesic]]s and/or [[anxiolytic|anti-anxiety medications]], although this is not a routine practice.
Typically, the aspirate is performed first. An aspirate needle is inserted through the skin until it abuts the [[bone]]. Then, with a twisting motion, the needle is advanced through the [[cortical bone|bony cortex]] (the hard outer layer of the bone) and into the marrow cavity. Once the needle is in the marrow cavity, a syringe is attached and used to aspirate ("suck out") liquid bone marrow. A twisting motion is performed during the aspiration to avoid a too high content of blood in the sample, which might be the case if a too large sample from one single point is taken.
Subsequently, the biopsy is performed if indicated. A different, larger [[trephine]] needle is inserted and anchored in the bony cortex. The needle is then advanced with a twisting motion and rotated to obtain a solid piece of bone marrow. This piece is then removed along with the needle. The entire procedure, once preparation is complete, typically takes 10-15 minutes.
If several samples are taken, the needle is removed between the samples to avoid blood coagulation.
==After the procedure==
After the procedure is complete, the patient is typically asked to lie flat for 5-10 minutes to provide pressure over the procedure site. After that, assuming there is no bleeding seen, the patient can get up and go about their normal activities. [[Paracetamol]] (acetaminophen) or other simple analgesics can be used to ease soreness, which is common for 2-3 days after the procedure. Any worsening pain, redness, fever, bleeding or swelling may suggest a complication.
==Contraindications==
There are few [[contraindications]] to bone marrow examination. The only absolute reason to avoid performing a bone marrow examination is the presence of a severe bleeding disorder which may lead to serious bleeding after the procedure. If there is a skin or soft tissue infection over the hip, a different site should be chosen for bone marrow examination. Bone marrow aspiration and biopsy can be safely performed even in the setting of extreme [[thrombocytopenia]] (low [[platelet]] count).
==Complications==
While mild soreness lasting 12-24 hours is common after a bone marrow examination, serious [[complication (medicine)|complications]] are extremely rare. In a large review, an estimated 55,000 bone marrow examinations were performed, with 26 [[serious adverse event]]s (0.05%), including one fatality.<ref>{{cite journal |author=Bain BJ |title=Bone marrow biopsy morbidity and mortality |journal=Br. J. Haematol. |volume=121 |issue=6 |pages=949–51 |year=2003 |pmid=12786808 |doi=10.1046/j.1365-2141.2003.04329.x}}</ref> The same author collected data on over 19,000 bone marrow examinations performed in the [[United Kingdom]] in 2003, and found 16 [[adverse event]]s (0.08% of total procedures), the most common of which was bleeding. In this report, complications, while rare, were serious in individual cases.<ref>{{cite journal |author=Bain BJ |title=Bone marrow biopsy morbidity: review of 2003 |journal=J. Clin. Pathol. |volume=58 |issue=4 |pages=406–8 |year=2005 |pmid=15790706 |doi=10.1136/jcp.2004.022178}}</ref>
==References==
{{reflist}}
==External links==
* [http://www.pathology.vcu.edu/education/lymph/How%20to%20Marrow.pdf An Illustrated Guide to Performing the Bone Marrow Aspiration and Biopsy (PDF)]
* [http://www.nlm.nih.gov/medlineplus/ency/article/003934.htm MedlinePlus: Bone marrow biopsy]
* [http://www.emedicine.com/med/topic2971.htm eMedicine: Bone Marrow Aspiration and Biopsy]
[[Category:Medical tests|Bone marrow examination]]
[[Category:Hematology|Bone marrow examination]]
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