How Should GPs Assess Fracture Risk?
The 'gold standard' for diagnosing osteoporosis is by measuring bone mineral density (BMD) using dual X-ray absorptiometry (DXA) and comparing the patient's result with that of a young adult of the same sex. In terms of standard deviations relative to the young adult normal, this is known as the T-score. BMD measurement is an important part of clinical decision-making and more information about the role of DXA scanning is given in 'How should GPs use bone densitometry?'. Bone density, however, is not the only indicator for fracture risk and 25% of women suffering a hip fracture do not have a T-score in the osteoporotic range. Age, previous history of fragility fracture and family history are risk factors for future fractures, independent of BMD. When using a fracture risk assessment tool, the National Osteoporosis Society recommends assessing BMD before commencing treatment.
There are several fracture risk assessment tools, including FRAX(r) and QFracture, in the NICE short clinical guideline CG146 - Osteoporosis: Assessing the risk of fragility fracture, published in August 2012. Those at risk should be identified opportunistically, either because they have already suffered a fracture or because they have a clinical risk factor or disease associated with a low BMD. FRAX(r) is likely to overestimate fracture risk in patients who are already taking an osteoporosis treatment and fracture risk may be underestimated in patients with clinically apparent vertebral fracture, who have had multiple fragility fractures or where there has been high exposure to corticosteroids, alcohol or smoking. More information on the limitations of FRAX(r) is given by the International Society for Clinical Densitometry. As with any assessment tool or guidance, clinical judgement should always be used. The following table, taken from CG146, summarises the risk factors included in both tools (as of April 2012):
|Age||30-84 years||40-90 years|
|Parental history of hip fracture||Yes||Yes|
|Hormone replacement therapy||Yes||No|
|History of falls||Yes||No|
|Chronic liver disease||Yes||No|
|Type 2 diabetes||Yes||No|
|BMD (femoral neck T-score/absolute risk||No||Yes (optional)|
*e.g. type 1 diabetes, chronic hyperthyroidism, premature menopause, chronic liver disease, chronic malnutrition, chronic liver disease
Treatment thresholds have been proposed by the National Osteoporosis Guideline Group (NOGG) for use with the FRAX(r) calculated 10-year risks. These are based on fracture risks in the previous Royal College of Physicians guidelines. For more information on the NOGG guideline are available within the Initiation section. QFracture proposes thresholds based on the top 10% at highest risk:
- For women, the cut off for the top 10% at highest risk is 10-year risk of 11.1%
- For men, the cut off for the top 10% at highest risk is 2.6%