Bone Marrow Aspirates and Biopsies
Clinical Significance and Indications
A bone marrow examination is an important part of the diagnostic work up for many hematologic disorders. Common indications for this procedure include unexplained cytopenia (i.e., anemia, leukopenia, or thrombocytopenia), suspected malignancy, staging of malignant lymphoma, assessment of response to chemotherapy, and the evaluation of patients with fever of unknown origin.
The handling of bone marrow specimens is technically demanding. Basically, the sample is obtained by inserting a hollow core needle into the soft center of the bone and withdrawing a sample. Two types of bone marrow samples include aspiration and biopsy.
Bone Marrow Aspiration
- Blood cells within the marrow are in a liquid state and can be aspirated through the needle and into a syringe. This can be performed either in the sternum with a smaller needle or in the iliac crest of the pelvis with a larger needle.
- Usually, the two syringe technique is recommended, which involves first withdrawing a small sample of concentrated bone marrow for direct smears and cytogenetics.
- Next, a larger volume of dilute marrow is sampled for special studies.
- Direct smears must be made quickly since fluid marrow clots readily.
- A portion of the aspirate should always be placed in an EDTA tube, so that back-up smears can be prepared.
- A number of special studies can be performed on the aspirate specimen, including chromosomal analysis (cytogenetics), immunophenotyping (flow cytometry) and culture. It is important to know which of these special studies is needed before the procedure begins so appropriate tubes and containers are available.
Bone Marrow Biopsy
Bone marrow collection can only be performed in a larger bone such as the iliac crest. An actual solid core of bone is obtained rather than a liquid sample. Touch preparations of the core can be obtained, and the rest is then fixed for histologic examination.