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Perth Haematology :: Dr Steven Ward

Bone Marrow Examination

 

Bone marrow examination is the test performed by Haematologists to obtain a sample of marrow to study the cells within the marrow. It is a very important test, often yielding the answer to the cause of the blood problem (i.e. providing the diagnosis).

 

The procedure is relatively straight-forward. The whole process takes 5-15 minutes. There is some discomfort but nothing severe. Two samples are usually taken from the back of pelvic bone using local anaesthetic.

 

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Patient positioned on their side on a bed or examination couch, with knees bent up.

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Local anaesthetic is injected into the skin and surrounding tissues down tot he edge of the bone (periostium). This is exactly like any other local - it stings and tingles for a minute before the area goes numb.

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Once the anaesthetic has taken effect (2 minutes usually) the patient will still feel things touching or a weird pressure feeling. This is because a small area of skin and the pelvic bone has been numbed, and the rest of the bone feels pressure. A small nick in the skin (3-4mm) is made to allow the easy passage of the marrow needle.

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The marrow aspirate needle is passed through this nick and gently doen to the edge of the bone. The needle is then pushed by a twisting motion into the bone. A pressure discomfort is often felt during this.

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Marrow is then aspirated by sucking hard on a syringe connected to the needle. This will often cause a short sharp pain down the leg, lasting only a split second.

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The needle is removed and a second needle inserted to allow a trephine to be taken. The procedure is similar to the first part, but involves only pushing and twisting without any sucking. A core of bone plus marrow is obtained.

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Once bleeding from the skin has settled a dressing or plaster is applied.

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Afterwards a dull ache is common. This can last 12-48 hours. Avoidance of strenuous exertion and paracetamol will help.

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The dressing is usually removed at home the following day.

 

Marrow Aspirate: obtaining marrow cells (liquid) for spreading onto slides and examination by microscope. This is almost always the most important part. The various marrow cell numbers and appearance (morphology) is assessed in detail.

 

Marrow Trephine: the core sample containing bone and marrow cells. This sample is useful as it preserves the normal marrow architecture so cells are positioned as they are within the marrow, also all cells are usually obtained (the aspirate can occasionally fail to obtain cells due to scarring or other difficulties). The trephine is useful in determining the pattern of disease involvement.

 

Additional tests performed on marrow: Often extra tests are required to confirm or aid the diagnosis. These are Immunophenotpying (or flow cytometry) to assess the immunological characteristics of the various cells; Cytogenetics (including FISH) invloves preparing chromosomes from the marrow cells to identify any abnormalities. Microbiological culture of marrow is occasionally useful (eg in diagnosis of Mycobacterial infections, TB).