Categories: Cancer

What is the function of bone marrow? How are bone marrow tests done?

Bone marrow is a spongy, gelatinous tissue found at the core of several bones in the body. Bone marrow is of two types – red and yellow. Red marrow, known as myeloid tissue, is found at the ends of the bones, while the yellow marrow, called fatty tissue, is found in the central, columnar part of the bone. Both red and yellow marrow are enriched with capillaries and blood vessels.

You may have heard of stem cells in recent years. These are immature cells found in the bone marrow that can develop into different types of cells. There are 2 types of stem cells – mesenchymal and hematopoietic. Yellow marrow contain mesenchymal stem cells, also called marrow stromal cells, which produce fat, cartilage and bone tissue.

Red marrow contains hematopoietic stem cells which are basically blood-forming stem cells. Most blood cells in the body develop from these stem cells, with as many as 220 billion of them being formed every day.

The blood-forming stem cells from the red marrow eventually mature and develop into three types of blood cells, each with their own distinct function.

Red blood cells or erythrocytes which transport oxygen throughout the body.
White blood cells or leukocytes that are responsible for our immunity, as they help fight infection and disease
Platelets or thrombocytes that help clot the blood after an injury so that blood-loss is minimized

Why are bone marrow tests done?

Bone marrow is extracted from the body and tested for any of these reasons:

Diagnose and monitor blood disorders, such as anemia, polycythemia vera, leukopenia, thrombocytopenia, pancytopenia and thrombocytosis, in which too many of a particular type of blood cells are produced
Diagnose bone marrow diseases such as myelodysplastic syndrome and myelofibrosis
Diagnose and monitor certain cancers such as leukemia, multiple myeloma, and lymphoma
To check for (confirm or rule out) anemia, or a low red-blood-cell count
To check iron levels in the body
To determine the cause for anemia (low rbc) and thrombocytopenia (low platelets)
To determine the cause for hemochromatosis, a genetic disorder in which iron levels in the blood shoot up
To investigate infection or a fever of unknown origin
Diagnose infections that may have started in, or spread to – the bone marrow
To check for cancers that have spread to the bone marrow (metastasized) from nearby
Determine the stage or progression of a disease
Detect abnormal chromosomes to understand risk of some diseases and accordingly plan treatment
Evaluate the person’s response to treatments such as chemotherapy and hence determine its success

Also Read: What Is The Difference Between Radiation Therapy And Chemotherapy?

How are the tests done?

There are 2 types of bone marrow – the liquid tissue and the solid tissue. The liquid is extracted using a thin and hollow needle, with the procedure being called aspiration. The solid bone marrow tissue is extracted through a thicker and hollow needle, with the procedure being called core biopsy or just biopsy. Generally, these 2 procedures are done at the same time.

Preparing for the procedure

Before the procedure is done, the doctor will evaluate the person’s family and personal medical history. More specifically, he/she will want to know if the person is allergic to chlorhexidine, local anesthetics, latex which is a type of rubber and adhesives such as tape. The doctor must also be told if the patient has had a heart-attack or stroke recently and is taking blood thinners currently. The doctor will want to know all the medication being taking currently such as over-the-counter drugs, prescribed medicines, vitamin supplements, herbal and alternative medicines. Female patients who are pregnant or suspect the same must mention this to the doctor.

The Procedure

The patient is fitted with a gown, laid on an operating table or bed. He/she is turned on the side if the samples are being taken from the hip-bone (pelvic aspiration/biopsy) or laid on the back if sample is being taken from the chest bone (sternal aspiration/biopsy).

Inserting the needle for both procedures can cause a sharp pain, which is why in most cases, the procedures are done under local anesthesia. Patients with a low tolerance for pain can additionally ask for mild sedation so that he/she is not awake or conscious in that time. Once the sample has been extracted, and the needle drawn out, the doctor will apply pressure on the spot to stop bleeding, and dress-up the wound.

The procedure is done at a clinic or hospital, with the patent being discharged the same day, once the effect of the sedative wears off. Its advised for the patient to be accompanied by a friend or family member after discharge and not drive back home.

Once the person is discharged, he/she must keep the wound dry for at-least 24 hours, which means, swimming, showering or sitting in a hot tub is restricted. The person must make follow-up visits to change the dressing. He/she must also reach out to the doctor if there is bleeding, redness, swelling and pain in that area, or fever.

Risks from the procedure

Both bone-marrow aspiration and biopsy are safe but a very small percentage (1%) of the patients may develop some complications such as:

Excessive bleeding: This is common in people with a low platelet count
Infection at the site: This is common in people with a weak or compromised immune system
Prolonged discomfort at the site
Heart or lung problems: This is even more rare and happens when the heart or lungs have been accidentally grazed while doing a sternal aspiration/biopsy.

Evaluating the results

The samples are sent to a diagnostic laboratory. Here, a pathologist or hemato-pathologist will look at the results and shall be able to say if the person’s bone marrow is producing enough healthy cells, and/or if any abnormal cells are present. This shall help the doctors confirm or rule out a disease and understand what stage it is in. And for patients who are undergoing treatment for some condition, the tests will reveal how effective the treatment is.

Reviewed by Dr Suresh S Venkita, Group Medical Director, Kauvery Hospitals

Kauvery Hospital is globally known for its multidisciplinary services at all its Centers of Excellence, and for its comprehensive, Avant-Grade technology, especially in diagnostics and remedial care in heart diseases, transplantation, vascular and neurosciences medicine. Located in the heart of Trichy (Tennur, Royal Road and Alexandria Road (Cantonment), Chennai, Hosur, Salem, Tirunelveli and Bengaluru, the hospital also renders adult and pediatric trauma care.

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