Skills Laboratory: How to collect diagnostic bone marrow samples - Veterinary Medicine
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Skills Laboratory: How to collect diagnostic bone marrow samples
Bone marrow evaluation can help reveal the cause of abnormal blood work results and much more. Get good samples by following these steps for bone marrow aspiration and core biopsy.


Figure 7. Once the needle is firmly seated in the medullary cavity, remove the cap, and withdraw the stylet.

Figure 8. Rapidly apply suction (8 to 10 ml). As soon as a flash of blood appears in the hub of the syringe, immediately release the suction to prevent hemodilution, a common cause of poor-quality samples.
After removing the stylet (Figure 7), attach a 10- or 12-ml syringe to the end of the biopsy needle. Rinsing the syringe barrel with 4% disodium- or dipotassium-EDTA reduces sample clotting during collection. Rapidly apply full suction (pull the syringe plunger to 8 to 10 ml) until the briefest flash of blood is seen (Figure 8), and then immediately release the vacuum. Immediate cessation of suction is crucial to preventing hemodilution. Gently remove the syringe, and expel the contents onto glass slides or into a watch glass containing EDTA. Alternatively, the entire needle with the syringe attached can be removed from the bone, and the contents of the syringe and needle can be expelled onto glass slides or into a watch glass.

Figure 9A. Express a small amount of marrow onto a slide, and tilt the slide to allow excessive blood to flow away from the spicules.
If you place the marrow sample onto glass slides, work quickly to prepare the slides to avoid sample clotting; it is helpful to have a second individual assist with slide preparation. Tilt each slide to allow blood to run off the slide (Figure 9A), place a second clean slide perpendicularly to the first slide, and use it to gently squash the marrow particles or spicules (Figure 9B). Gently pull apart the two slides, spreading the marrow spicules across the slides.

Figure 9B. Place a second slide on top of the spicules perpendicular to the first slide, and gently squash the spicules as you pull the second slide across the first.
If you place the sample in a watch glass, tilt the container to allow the blood to drain away, revealing marrow spicules. Marrow spicules look like pale yellow, glistening grains of sand. Gently retrieve the spicules with the end of a pipette, microhematocrit tube, or hypodermic needle. Place the spicules on a glass slide, and gently crush them with a second clean glass slide. The marrow and blood remaining in the watch glass can be transferred to an EDTA vial and submitted with the smears in case additional slides need to be prepared. Clotted marrow samples can be placed in formalin and processed like a biopsy sample.5

Figure 10. The unstained slide (left) has several light grainy areas (arrow). The light areas are the squashed marrow particles surrounded by blood. The stained smear (right) contains deeply basophilic cellular spicules surrounded by blood.
Allow the smears to dry before staining. Marrow spicules on an unstained slide appear as light grainy areas (Figure 10) and are usually surrounded by blood.


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