The bone marrow makes blood cells and platelets. It is a soft fatty tissue found inside the hollow shafts of bones such as the breastbone (sternum), hip bone (pelvis) and thigh bone (femur). Fibrous tissue in the bone marrow forms a sponge‑like network that supports the production of stem cells, which produce all types of blood cells.
A number of conditions can affect the structure and function of bone marrow. This in turn can affect the production and function of blood cells and platelets. Bone marrow testing may be used to inform the diagnosis of these conditions, determine the efficacy of treatments, and monitor the recovery process. It is also an essential part of the staging process for people newly diagnosed with certain types of cancer. Bone marrow testing is also used to determine the extent of marrow damage among people who have been exposed to radiation, drugs, chemicals, and other agents that damage bone marrow. Some people will have several bone marrow examinations to help healthcare professionals to monitor and manage disease progression.
In 2012, 29,785 people were newly diagnosed with cancers that needed bone marrow testing (Office for National Statistics 2012). These included:
12,412 people with lymphomas
7422 people with leukaemias
4190 people with myelomas
412 people with bone cancers.
These cancers are slightly more common in men (56% of cases), and 52% of all cancers are diagnosed in people aged over 70 years. However, these diseases also impact disproportionately on children and young people, with leukaemia the most common childhood cancer. In total these cancers account for over 50% of all cancers in children and young people aged 14 years and under (593/1170).
Five‑year survival rates for adults vary from 37% for people with myeloma, to 83% for people with Hodgkin's lymphoma (Cancer Research UK 2014).
The Hospital Episode Statistics for England (Health and Social Care Information Centre 2014) reported that 44,207 bone marrow tests were performed in 2012/13. The mean age for the procedure is 57 years, with more men than women having tests (59% versus 41%). The tests were performed as follows:
29,430 (66.6%) people had tests as day cases
11,752 (26.6%) people had tests as inpatients
3025 (6.8%) people had tests as outpatients, of which 379 (0.9%) people had the tests on their first attendance.
There are 2 techniques for extracting bone marrow for testing:
Bone marrow aspiration – a small, hollow needle is used to draw out about 1–20 millilitres of bone marrow. In adults, this is taken from the iliac crest area of the pelvis. For infants and younger children other bones such as the shin bone (tibia) may be used.
Bone marrow biopsy (trephine) – a small sample of marrow ('core') is extracted from the same bones as for aspiration, but using a needle with a thicker bore.
People usually have both kinds of test, although occasionally only an aspirate sample is needed. The aspirate sample is used for cytological evaluation and the biopsy sample for histological evaluation. Results from the cytological evaluation are usually available in 2 days, but results from the histological evaluation take around 10 days.
Bone marrow extraction can be challenging for the healthcare professional carrying it out. In addition, people can experience varying degrees of pain during the procedure, which may make them reluctant to have repeat tests. Health care professionals usually inject a local anaesthetic into the skin over the pelvis, to numb the area the sample will be taken from. Some hospitals offer adults sedation for repeat tests if they found a previous test painful. Children are usually offered general anaesthesia.
If the volume and quality of the bone marrow removed is not adequate for testing then the extraction will need to be repeated, potentially delaying the diagnosis and increasing the pain experienced by the person having the test. The international guidelines on the standardisation of bone marrow specimens advise that the core length of bone marrow biopsies taken from an adult should be at least 2 cm. The guideline states that a shorter core (for example 1 cm) can sometimes contain enough tissue to make a diagnosis, but that longer cores allow for greater diagnostic accuracy of a larger range of conditions (Lee et al. 2008).
A great deal of pressure has to be applied to the needle in bone marrow aspiration and biopsy, to force it through the outer bone and into the marrow cavity. This can make the procedure difficult to perform, and difficulty in completing the procedure is associated with poorer sample quality (Bishop et al. 1992).