Why measuring absolute risk of fracture could save many broken bones
Media Release: 28 July 2009
A person's absolute risk of fracture over the next 5 or 10 years can be predicted with reasonable accuracy according to their age, sex, bone density and history of fractures and falls.
While not an exact science, risk predictions allow people to make more informed choices about whether or not they will seek or accept treatment.
In Australia, the Government pays for preventative treatment based primarily on whether or not someone has already sustained a fracture. The problem with this approach is that many of those at high risk of future fracture have no history of prior fracture.
The Government also provides treatment for those 70 years or older with very low bone density, even without a fracture, and in some other situations such as high-dose, long-term corticosteroid use.
However, over 50% of women and 70% of men who fracture do not have osteoporosis, and do not have any prior history of fracture. So many people at high risk of fracture are not aware of their risk, and nor are their doctors. If they were aware of that risk, they may decide to make lifestyle changes, or pay for treatment themselves.
Dr Sunita Sandhu, Professor Tuan Nguyen, Professor John Eisman and Dr Nguyen Nguyen from the Garvan Institute of Medical Research have compared the performance of Garvan's fracture risk calculator (www.fractureriskcalculator.com), launched early last year, with one released by the World Health Organisation (WHO). Their findings are published in Osteoporosis International, now online.
In a 'matched case-control study', 69 women with a fracture were matched against 75 women without a fracture, and 31 men with a fracture were matched against 25 men without a fracture.
"We can see very clearly that our model predicts fracture at least as well as the WHO model when applied to an Australian population, and apparently more accurately for Australian men," said Professor Nguyen.
The Garvan fracture risk calculator is based on gender, bone mineral density, age, history of personal fracture, and history of falls.
The WHO model ignores falls, but includes height, weight, personal history of fracture, family history of fracture, smoking, alcohol consumption, use of corticosteroids, rheumatoid arthritis and secondary osteoporosis.
According to Professor Nguyen, "the results suggest that the criteria in the Garvan calculator combine the most critical risk factors."
"Our model allows clinicians to combine four risk factors to estimate the risk of fracture within the next 5 to 10 years for an individual man or woman. People can then make decisions about treatment based on that knowledge."
"In the future we will be able to incorporate genetic information as a useful additional criterion, once we have more clearly established which genes are involved in fracture risk."
"In other fields such as cardiovascular diseases and cancer, treatment is now based on an individual's absolute risk of having a disease. In osteoporosis, we are gradually moving in that direction."