ReviewIndividualizing fracture risk prediction
Introduction
The World Health Organisation (WHO) has defined osteoporosis as ‘a disease characterised by low bone mass and microarchitectural deterioration of bone tissue, leading to enhanced bone fragility and a consequent increase in fracture risk [1].’ Bone mass and bone mineral density (BMD) are most commonly measured by dual energy X-ray absorptiometry (DXA), a validated technique for measuring BMD in the lumbar spine and proximal femur. The outcome of the DXA-measurement is expressed as a T-score (T-score = (measured BMD − young adult BMD)/young adult SD). The cut-off point for osteoporosis is a T-score of 2.5 standard deviations (SDs) below the mean BMD, at the spine or at the hip, in a healthy female population aged 30 years [1], [2], [3], [4]. Approximately 15–20% of all postmenopausal women are defined as osteoporotic, using the diagnostic threshold of a T-score ≤ −2.5 measured with DXA at the femoral neck (FN) or lumbar spine [5].
However, most patients with a fracture have no osteoporosis [6]. Many clinical risk factors (CRF) have been identified predict fracture risk, independently of each other and of BMD [7], [8]. By integrating CRFs and BMD in case-finding strategies, the risk of fracture at any BMD will also depend on the presence of CRFs. Intervention thresholds based on fracture risk calculations can therefore be different from the WHO diagnostic thresholds [9].
We review recent developments in case-finding strategies, which can be used in daily practice to calculate fracture risk in individual patients.
Section snippets
The clinical significance of fractures
The clinical significance of osteoporosis is the occurrence of fractures. Hip fractures increase morbidity and mortality and entail high socio-economic costs [3], [4], [10]. Estimates show that, in Europe alone, 890,000 persons (80% women) sustained a hip fracture (24% of total number of fractures) in the year 2000. The number of hip fractures alone could increase to 6.3 million by the year 2050 or even to 8.2 million if the assumption is made that the age-related incidence of hip fractures
Individualizing fracture risk prediction
Earlier guidelines on osteoporosis by the National Osteoporosis Foundation (NOF, in the US) and the National Osteoporosis Society (NOS, in the UK) were mainly aimed at selecting patients with pre-existing fracture or low bone mineral density for treatment [16], [17]. However, the occurrence of a fracture is a multifactorial event. Consequently, there is more than one way that an individual can attain the risk conferred by either osteoporosis or a pre-existing fracture and many CRFs have been
The fracture risk assessment tool (FRAX) [20]
The World Health Organisation (WHO) [2], [20] has developed an algorithm for individualized fracture risk prediction which is developed based on population-based cohorts from Europe, North America, Asia and Australia. The algorithm in FRAX includes the following risk factors: [4], [7], [21], [22], [23], [24], [25], [26], [27], [28], [29], [30], [31], [32], [33], [34], [35], [36], [37] age, a history of fractures, a parental history of hip fracture, low body weight or body mass index (BMI), use
Comparison of the FRAX and Garvan fracture risk calculator
Comparisons between the FRAX and Garvan tool are shown in Table 2, Table 3 and Fig. 1, Fig. 2, Fig. 3, Fig. 4. In patients without clinical risks, the fracture risk calculation for osteoporotic fractures is higher with the Garvan tool than with FRAX, since the Garvan tool predicts more fractures that FRAX (Table 2, Table 3).
The effect of fracture history on calculated fracture risk is shown in Table 2, Table 3 and Fig. 1. Calculated fracture risk increases with both tools in patients with a
Website versions
Both fracture calculations tools are freely accessible on the internet and easy to use online at the respective websites [20], [51]. The introduction of risk factors is self-explanatory and comments are available explaining in detail the definitions of CRFs.
Paper-based versions
The FRAX has simplified paper-based models in tabular format available on the website. These tables are not CRF specific, but state the risk for up to 6 CRFs for age per 5 years (range 50–90 years) and the BMD T-score per 0.5 SD (range −4.0
Conclusions
The FRAX and the Garvan fracture risk calculator are both widely available tools for individualized fracture risk prediction in daily practice. The FRAX model is implemented in the NOF, NOS and NOGG guidelines and most widely used at present. Both models still need to be validated in different populations before they can be generalized to other populations, since the background risk for fractures is population specific. Clinicians should take into account the differences between the models
Contributors
Tineke van Geel is the principle investigator and the main author of the manuscript. Piet Geusens and Geert-Jan Dinant are the supervisors of the principle investigator and responsible for the medical and scientific content of the manuscript. Joop van den Bergh has contributed substantially to the intellectual content of the manuscript. All authors have read and approved the manuscript and agree with publication of their names.
Conflict of interest
All authors report no conflict of interest.
Provenance
Commissioned and externally peer reviewed.
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