A bone density test, also known as bone mineral density test, is a specialized diagnostic assay that identifies if the individual has developed osteoporosis, a debilitating illness wherein bone tissues become fragile and break. Osteoporosis, being a silent ailment, does not present with any perceivable or substantial symptoms in the initial stages and only demonstrates weak, porous bones which have incurred considerable damage in the later phases. A bone density test is very useful in these instances to spot the risk factors of osteoporosis early on and provide pertinent medical treatment to help restore bone strength and structure.
The fundamental supporting parts of the body, there are 206 bones in adults, which are mineralized connective tissues. Bones carry out many crucial functions in the system, such as providing a stable structure, safeguarding key internal organs, permitting smooth organized movement and locomotion. Moreover, they house the bone marrow, wherein new blood cells are synthesized and work as a primary storage area for essential minerals, chiefly calcium. It is this inherent calcium content that contributes to the rigidity, durable assembly of all healthy bones and which is measured in the bone density test to determine how tough the connective tissues are.
Why It Is Done:
The main purpose of the bone density test is to discern the risk of osteoporosis by recognizing reduced thickness of skeletal constructs in time and thereby preventing them from breaking. It also has various other uses such as:
- Identifying if an individual is prone to fractures
- Verifying a preliminary diagnosis of osteoporosis
- Observing the progress of osteoporosis treatment in affected persons
Additional reasons to perform the bone density test include:
- Women who have attained menopause and are above 50 years old
- Adult women showcasing irregular periods without being in pregnancy or menopause
- Older men with weak bones over the age of 50
- Undergoing a decrease in height during adulthood by more than 1.5 inches
- Experiencing persistent back pain despite not having undergone any falls, strain or other trigger factors
- Developing a slouched posture with a prominent hunch in adulthood
- Detecting lower levels of hormones in the system, namely estrogen in women due to increasing age or cancer treatment and testosterone in men from growing older or undertaking radiation therapy
- Having suffered a fracture recently, especially in old age
- Taking potent prescription steroid medications over a long period of time
How To Prepare:
A bone density test is a quick and simple process that requires very minimal preparation. Individuals need not go on fasting but must ensure that they have not consumed any calcium supplements in the last 24 hours prior to taking the bone density test. Also, people who have been injected with a contrast dye for CT/MRI scans or have taken a barium test are advised to wait for 7 days before going for a bone density scan, as the infused materials could interfere with the readings.
It is recommended to wear loose-fitting clothes which are a comfortable fit, not too tight and do not have fasteners with metal elements, like zips, hooks, buttons. If donning any belts, watches, jewellery or having any keys, coins in the pockets, the individual will be asked to keep them aside before taking the bone density test. Nevertheless, to clearly view the internal structure of the bones, sometimes the patient is asked to remove their clothing and wear a clean loose gown provided by the healthcare facility.
The investigative process of a bone density test is a basic painless scan involving an X-ray, which evaluates the amount of calcium and other minerals in a particular segment of the bones, primarily in the hips, forearm and spine. The bone density test is usually performed in a hospital or clinic setting with advanced medical equipment, by a doctor, nurse, radiologist, certified medical lab technician like a radiographer.
The patient is asked to lie down flat on the back, on a healthcare testing bed and to remain still without moving, while a huge scanning device passes on top over the body, to calculate the density of bones in the skeleton. Utilising a technique of Dual-Energy X-Ray Absorptiometry (DXA or DEXA), two very low-dose X-ray beams possessing varying energy concentrations are focused on the individual’s bones. These energy emissions are absorbed by the bone tissues and the signals are read and measured by an X-ray detector in the scanning arm. From this, a visual image of the scanned regions of the bones is obtained.
The bone density test does not present any known risks to the patient. The entire procedure of the DXA scan takes only between 10 – 20 minutes, being both painless and non-invasive. The individual can go home after taking the test and resume all normal day-to-day activities at home and work.
Furthermore, only very minor amounts of X-ray emissions are assimilated by the internal tissues during the course of the bone density test, so the risk of radiation exposure is very small and does not present with any grave complications. Pregnant women are however advised to not take the bone density test as X-ray beams could pose health threats to the developing foetus.
The results of the bone density test are usually available within one week after taking the X-ray scan. The test reports mention two distinct numbers known as T-score and Z-score.
T-score indicates the calculated bone density values compared to what is considered normal and healthy as per age and gender.
- T-score of -1 and above: Bone density is normal
- T-score between -1 and -2.5: Bone density is low and signifies osteopenia, a risk factor for osteoporosis
- T-score of -2.5 and below: Bone density is very less and indicates osteoporosis
Z-score measures the bone density of the patient in parallel with other individuals of the same age, gender and body weight/size. A Z-score less than -2.0 indicates low bone density which could be prompted by osteoporosis or other health anomalies and is not a usual aspect of ageing. Besides bone density test, additional diagnostic assays are also required to confirm the risk of fractures or the extent of osteoporosis.