In BMD test results, your bones are compared to the bones of an average young adult. A score (called a
T-score) is calculated that describes the density of your bones (usually at the spine and hip) and tells you
how strong your bones are compared to this average. While some bone loss with aging is considered normal,
making such comparisons helps to determine whether you are losing bone more rapidly than expected for someone
your age.
The T-score is expressed in units referred to as "standard deviations (SDs). These SD units tell us how
far you differ (or deviate) from what is considered normal for a young adult. "Below normal is always
indicated with a minus (-) sign. According to World Health Organization (WHO) classifications, a T-score
below 2.5 SDs indicates osteoporosis and a score between 1 and 2.5 SDs indicates "osteopenia or low bone
density. Normal bone density is no more than 1 SD below the young adult normal value. Your BMD test results
and the WHO classifications are only part of the picture in determining your risk for fracture.
Your BMD test results and the WHO classifications are only part of the picture in determining your risk
for fracture. Two 10-year fracture risk assessment tools are now available for Canadians:
CAROC
In 2005, Osteoporosis Canada, in association with the Canadian
Association of Radiologists, launched the 10-year absolute fracture risk assessment - CAROC.
In addition to BMD (lowest T-score of hip and lumbar spine), age, gender,
fracture history and steroid use are taken into consideration to determine an individual’s 10-year risk of
fracture.
The presence of both a fragility fracture and steroid use puts the
patient at high fracture risk regardless of BMD result.
Version 2, now available for Canadian physicians, uses only femoral neck
(hip) BMD rather than the lowest of hip and lumbar spine.
FRAX
In 2008, the World Health Organization (WHO) launched the FRAX tool (Fracture Risk Assessment) – www.shef.ac.uk/FRAX. In 2010 Canadian data were added to
this tool. In addition to femoral neck (hip) BMD, age, gender, fracture history and steroid use, FRAX also
takes into account other clinical risk factors to calculate the absolute 10-year risk of a hip fracture or
other major osteoporotic fracture (spine, forearm, upper arm). These factors include:
- BMI (weight to height ratio calculation)
- Other secondary conditions that contribute to bone
loss
- Alcohol intake (three or more drinks per day)
CAROC/FRAX?
The FRAX system is based upon a more complete set of clinical risk
factors and it can be used without BMD results; but it requires access to FRAX software, website or paper
chart.
CAROC is less complete but captures the major risk factors for fracture
and is easy to use.
For the majority of people, the results are the same regardless of which
of these tools is used. Therefore the choice of FRAX or CAROC by the clinician is a matter of personal
preference and convenience.
