Bone marrow examination

Did You Know?

• Thrombocytopenia or bleeding disorders are not contraindications as long as the procedure is performed by a skilled clinician.
• If a skin or soft tissue infection is present over the hip, a different site should be chosen.

Components of the procedure

Bone marrow samples are obtained by aspiration and trephine biopsy, often both. Aspiration yields semi-liquid marrow (about 300 μL) examined by light microscopy, flow cytometry, chromosome analysis, or PCR. Trephine biopsy yields a solid cylinder (2 mm wide, 2 cm long) examined for cellularity and infiltrative processes, sometimes with immunohistochemistry. Volumes over 300 μL may dilute the sample with peripheral blood. Aspiration may miss cells like lymphoma that adhere to trabecula.

Site of procedure

The posterior iliac crest is the usual site for aspiration and trephine biopsy. Aspiration can also be done on the sternum, with the patient lying supine and a pillow under the shoulders. Trephine biopsy is never performed on the sternum due to risk to blood vessels, lungs, or heart. In children up to 2 years, tibial aspiration may be used. Spinous process aspiration is often done at L3-L4 in a lumbar puncture position. Local anesthesia reduces surface pain, but marrow pain cannot be anesthetized.

Test performance

The procedure may be done in a provider's office or hospital, typically after informed consent. The patient lies prone or in lateral decubitus position. The skin is cleansed, and local anesthetic (e.g., lidocaine or procaine) is injected. Pretreatment with analgesics or anti-anxiety medications is not routine. Aspiration is performed first: a needle is inserted through skin and bone cortex into the marrow cavity, then a syringe aspirates liquid marrow with a twisting motion to avoid excess blood. If biopsy is indicated, a larger trephine needle is inserted, advanced with twisting, and rotated to obtain a solid piece. The entire procedure takes 10–15 minutes after preparation. If multiple samples are taken, the needle is removed between samples to prevent blood coagulation. Afterward, the patient lies flat for 5–10 minutes for pressure. If no bleeding is observed, normal activities can resume. Paracetamol or simple analgesics ease soreness common for 2–3 days. Worsening pain, redness, fever, bleeding, or swelling may indicate a complication. Patients should avoid washing the site for at least 24 hours.

Complications

Mild soreness lasting 12–24 hours is common, but serious complications are extremely rare. In a large review of 55,000 procedures, 26 serious adverse events (0.05%) occurred, including one fatality. A UK review of over 19,000 procedures found 16 adverse events (0.08%), most commonly bleeding. Complications, while rare, were serious in individual cases.