At birth, all bone marrow is red, but with age, more and more of the red marrow converts to yellow marrow, so that by old age, yellow marrow is the predominant form

Chirawan Somsanuk | Dreamstime

Your recent blood tests have produced some troubling results. Maybe your red blood cell count is too low. Or, perhaps your platelet level is too high. In either case, your physician may order a bone marrow test to try to identify what’s causing these abnormalities or to diagnose other potential problems.

The test can provide information about several diseases of the bone marrow or blood cells, such as anemia. It also can be used to stage cancers of the blood or bone marrow, or to monitor treatment of certain diseases. Before you undergo a bone marrow test, it’s important to understand the function of bone marrow, the diseases that may be associated with it, and what you can expect from the test.

What Is Bone Marrow?

Bone marrow is spongy tissue found in numerous bones throughout the body that produces most of your blood cells. The marrow contains stem cells, the unspecialized cells that can develop into certain types of cells with specific functions, such as muscle cells and brain cells.

The marrow also contains erythroid cells, which form red blood cells; myeloid cells, which are precursors to disease-fighting white blood cells; and large cells known as megakaryocytes, which form the platelets that are vital for blood clotting.

Bone marrow is categorized into two types: red marrow and yellow marrow. Red marrow is responsible for producing blood cells and, in adults, is found especially in the pelvis, vertebrae, shoulder blades, ribs, sternum, and the ends of the longer bones of the body, such as the femur (thigh bone) and humerus (upper arm bone).

At birth, all bone marrow is red, but with age, more and more of the red marrow converts to yellow marrow, so that by old age, yellow marrow is the predominant form. Named for its coloring that results from its high fat content, yellow marrow produces cells involved in the formation of bone, cartilage, and fat.

Why You Need a Bone Marrow Test

A bone marrow test isn’t routinely ordered. Rather, your doctor may recommend it if results of other testing, such as a complete blood count, show abnormalities. The test may be necessary if your physician suspects you have certain malignancies or diseases affecting blood-cell production and bone marrow, based on your symptoms, physical exam, and your medical history:

• Cancer: An exam of the bone marrow may be necessary to determine the stage of certain cancers (how greatly they have advanced). These cancers include leukemia, cancer of the bone marrow and other blood-forming tissues that results in overproduction of abnormal white blood cells; lymphoma, a type of cancer originating in certain immune cells of the lymph system; and multiple myeloma, cancer that originates in immune cells known as plasma cells and can form bone tumors.
• Secondary cancers: Some cancers, such as breast and lung cancer, can spread to the bone and bone marrow.
• Anemia: Anemia is a lack of red blood cells or hemoglobin in the blood. Some forms of anemia result from bone marrow or stem cell problems.
• Iron deficiency: Your body needs iron to make hemoglobin, a key component of red blood cells that carries oxygen throughout the body. Bone marrow is a storage area for iron. In rare cases, a bone marrow test may be necessary to assess iron levels in the body if routine blood tests and other exams fail to uncover the cause of iron deficiency.
• Other blood cell disorders: Testing bone marrow can help diagnose disorders resulting in production of too few or too many platelets (thrombocytopenia and thrombocytosis); white blood cells (leukopenia and leukocytosis); and red cells, white cells, and platelets (pancytopenia and polycythemia).

Additionally, your healthcare team may assess your bone marrow to determine the effects of cancer treatment on bone marrow function and measure your response to treatment.

What a Bone Marrow Test Entails

A bone marrow test is done in two parts—a bone marrow biopsy and aspiration—and can be performed at your physician’s office or a hospital. Usually, the test is done on the pelvic bone.

With aspiration, the physician numbs the area with local anesthetic and then inserts a needle syringe into the bone to retrieve a small sample of liquid bone marrow. For the biopsy, the doctor uses a needle to obtain a tiny sliver of bone filled with marrow. These tissue samples are reviewed under a microscope, and the aspirated liquid may be sent for further cellular analysis.

Bone marrow biopsy and aspiration is generally safe, but like any invasive test, it does carry some risks, such as infection, bleeding, or bruising in or around the biopsy site. The biopsy and aspiration procedure may cause some discomfort, and you’ll feel some slight pain once the anesthetic wears off. For some patients, the soreness at the biopsy site lingers for a few days. Most patients can return home immediately after the procedure.