- Mark J Bolland, senior research fellow1,
- Rod Jackson, professor of epidemiology 2,
- Greg D Gamble, research fellow1,
- Andrew Grey, associate professor of medicine1
- 1Department of Medicine, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
- 2Section of Epidemiology and Biostatistics, University of Auckland
- Correspondence to: M Bolland
- Accepted 3 December 2012
Doctors are increasingly using calculators to estimate the absolute risk of fracture in their patients, but we have noticed large differences between risk estimates from different calculators. Specifically, the FRAX calculator can give surprisingly low 10 year estimates of fracture risk in older patients with known risk factors, often much lower than those generated by other fracture risk calculators. When considered alongside guidelines for treatment, these lower estimates could lead to elderly people not being offered treatment. We explain the reasons for the differences in estimates and discuss the implications for clinicians.
Fracture risk calculators
Several calculators have been developed to estimate risk of fracture, of which FRAX, the Garvan calculator, and QFracture, are most widely used (table 1⇓). They are an important advance in the care of patients with osteoporosis because management decisions no longer have to be based solely on bone mineral density. Each calculator was derived from prospective cohort studies, has been validated by independent investigators, and has moderate predictive ability for osteoporotic fractures and moderate to good predictive ability for hip fractures.1 2 3 4 The important differences are the time frame for the estimation of risk and the approach to the competing risk of mortality. The Garvan calculator estimates five and 10 year risks of fracture, QFracture estimates risk of fracture for any whole year between one and 10 years, and FRAX estimates only 10 year risk of fracture. Only FRAX takes account of the competing risk of mortality.
Unlike the Garvan and QFracture calculators, the equations and algorithms underpinning FRAX and the specific methods used to take account of mortality have not been …