About Bone Mineral Densitometry
Bone Mineral Densitometry (BMD) or Bone Density is today’s established standard for measuring bone mineral density and diagnosing osteoporosis. These dual energy X-ray absorptiometry (DXA) scans are safe, painless and accurately measure bone density. The scan involves lying on a table while a small X-ray detector scans, most commonly, the spine & one hip, using a very small amount of radiation. The exam is approximately 15 minutes.
In BMD test results, bones are compared to the bones of an average young adult. A score (called a T-score) is calculated that describes the density of the bones measured. The T-score is expressed in standard deviations and tells us how the results deviate from what is considered normal for a young adult. The World Health Organization (WHO) classifies a T-score of < -2.5 SDs as osteoporosis. A score between -1 and -2.5 SDs indicates osteopenia or low bone density. Normal bone density is classed as anything above -1. The BMD results and the WHO classifications are only part of the picture in determining the 10-year fracture risk of the patient. The risk will be determined as low, moderate or high, considering the BMD results, age and gender. Other clinical factors, particularly a fragility fracture after age 40 or glucocorticoid use for more than three months, substantially elevate the fracture risk. The presence of either of these factors will increase the 10-year risk of fracture to the next level. If both of these particular factors were present, the risk would be considered high regardless of the BMD result.
Drug treatment can be monitored with a follow-up bone density scan. It is beneficial to be re-tested on the same BMD machine whenever possible to be able to accurately compare scans to get the best results.
