Bone Mineral Density Testing

Confirming an initial diagnosis

What is bone mineral density (BMD) testing?¹

Until recently, osteoporosis could not be easily diagnosed until a fracture occurred, but today, we have bone densitometry. Bone densitometry is a non-surgical method that is used to estimate bone strength and the likelihood that bones will fracture with simple trauma. The bone densitometry test:

• Uses very low or ultra low X-ray doses to examine a patient's bone density

• Is painless

• May be done using a central non-portable machine, or a smaller portable model

  • The central non-portable test is the more accurate test

• Is used as part of an overall total assessment to determine fracture risk and a diagnosis of osteoporosis or osteopenia

BMD value expectations²

Osteopenia:
T-score* between -1.0 to -2.5 SD below T-score norm

Osteoporosis:
T-score* of -2.5 SD or lower below T-Score norm

Severe Osteoporosis:
T-score* of -2.5 SD or lower below T-Score norm + fracture(s)

Bone density tests are divided into two types — central and peripheral¹

Central Machine Tests¹

• DXA (Central Dual Energy X-ray Absorptiometry)
• QCT (Quantitative Computerized Tomography)

Central Machine Tests are the current gold standard. This technology is most frequently used for measuring bone mass at the spine and/or hip and/or radius (sometimes the whole body). The examination consists of a very low dose X-ray to rapidly scan a patient's bones. A computer converts this information into numbers that indicate that patient's bone density.

Central testing can also be performed using quantitative computerized tomography (QCT) scanning, a more specialized type of computerized tomography (CT scan or CAT scan) that requires the use of much larger doses of X-ray radiation. However, this method is currently used only to measure the spine and is not directly comparable to other scanning techniques.

Peripheral Machine Tests¹

• pDXA (Peripheral DXA)
• QUS (Quantitative Ultrasound)
• pQCT (Peripheral QCT Scanning)

Peripheral Machine Tests measure BMD at skeletal sites such as the heel or finger through several technologies, including peripheral DXA (pDXA), quantitative ultrasound (QUS), and peripheral QCT scanning (pQCT). These tests may be used to help predict fracture risk or screen individuals for low bone mass. They can be particularly useful when central DXA is not available.

Current ISCD (International Society for Clinical Densitometry) recommendations suggest that they not be used to provide definitive diagnosis of osteoporosis, nor should they be used to monitor the effects of therapy. The ISCD believes that peripheral machine tests are less reliable and responsive than central machines. The ISCD recommends that if peripheral technology shows that an individual has low bone mass, that individual should have a central DXA performed for diagnostic purposes.

Click here for official ISCD positions.