One of the challenges in managing patients suspected of having osteoporosis and at increased risk of fracture is understanding how fracture risk assessment tools, bone densitometry, and the use of anti-osteoporosis therapies can fit together to benefit patients.
A check for the presence of risk factors is reasonable from the age of 50 years onwards because the prevalence of risk factors increases from this age upwards. Risk factors and the influence of sex can be incorporated into a better understanding of an individual’s risk through use of an absolute risk calculator. There are many clinical risk factors for fracture in addition to those included in FRAX® that can be used to trigger fracture risk assessment (e.g., inflammatory arthritis or coeliac disease). Several diseases (e.g., rheumatoid arthritis, thyroid disease) and medications (e.g., corticosteroids) on their own are also regarded as sufficient risks for osteoporosis to warrant BMD measurement. This implies the use of FRAX®-based risk estimation prior to BMD is most relevant to those weaker clinical risk factors and age (refer to the ‘Osteoporosis risk assessment, diagnosis and management flow chart’). Clinical judgment is needed when clinical risks exceed those that can be incorporated into a FRAX® assessment. This approach of recommending a BMD on the basis of FRAX® risk has been adopted in several countries.1 The use of a risk estimation tool such as FRAX® also removes the need to set different minimum ages for initial risk enquiry for men and women because sex is part of the risk estimation algorithm.
The absolute risk at which to recommend DXA and the threshold for treatment, especially pharmacotherapy, is important, yet not consistently defined. The level of risk perceived as ‘high’ will vary between individuals and may differ from the point of view of a funder. Bone density alone is not sensitive for predicting fragility fractures given that most fragility fractures occur in people in the osteopenic range. This can be improved by the use of absolute risk estimation tools, but at the expense of added complexity for the clinician. However, almost all anti-osteoporosis treatments have been studied in RCTs of patients with low BMD values and/or prior fracture rather than based on absolute risk estimation. Three trials allow an estimate of absolute risk at which treatment is effective, as detailed below.
In the Fracture Intervention Trial (FIT) trial (oral alendronate), which was effective at reducing fractures, 90% had a baseline 10-year fracture risk >14%, with virtually all having a risk >10%.10 In the Fracture Reduction Evaluation of Denosumab in Osteoporosis Every Six Months (FREEDOM) trial, the median baseline 10-year fracture risk was 15%.11 Denosumab seemed effective for those with a baseline 10-year fracture risk >12%.11 In the third trial, which evaluated zoledronate in osteoporotic women aged >65 years, zoledronate was effective, with a median baseline absolute risk of 12% for fracture at 10 years.12
The thresholds used in the screening trials can also inform the decision to refer for DXA. The ROSE study used a threshold of 15% 10-year fracture risk (FRAX®) to recommend DXA testing.3 The SCOOP trial used a range of age-specific thresholds (3.4% at 50 years, rising to 11.1% 10-year risk of major osteoporotic fracture at 70 years),2 which may make implementation in the Australian primary care setting difficult without clinical decision support software or a graphic reference of risk thresholds by age.
Given that case finding would be used for a population selected for their interest to engage in fracture prevention interventions, the impact can be expected to be better than demonstrated in the population screening trials. A slightly lower threshold for recommending BMD assessment has been adopted, as was done in the Scottish Intercollegiate Guidelines Network 2021,13 where a 10-year risk of major fracture of >10% triggers a recommendation for BMD measurement, which is relatively pragmatic and inclusive. A patient’s personal meaning and value placed on a risk estimate should also guide the next steps.
Economic modelling of potential population screening regimens suggests a higher risk threshold is needed to be cost-effective. The absolute risk thresholds for cost-effectiveness were similar across ethnic and racial groups, and slightly higher for men. This assumes five years of full medication adherence. A 2013 Japanese study suggested screening women with a 10-year risk of osteoporotic fracture >26% would be cost-effective at US$50,000/QALY.14
Evidence statement for population screening
The SCOOP RCT recruited woman aged 70–85 years from primary care practices in the UK and showed that a screening program using FRAX® first, followed by DXA in those at high risk of hip fracture (probability 5.2–8.5%, depending on age), was associated with a reduction in hip fracture incidence (hazard ratio [HR] 0.72; 95% CI: 0.59–0.89) compared with those undergoing usual care.2 However, there was no reduction in the prespecified primary outcome of all osteoporosis-related fractures. The use of bone-protective therapy was also higher in the screened group and, in subsequent analysis, medication adherence was increased, even out to 60 months.5 Of note, fracture probability was then recalculated using the BMD result, and those with a fracture risk above the intervention threshold (hip fracture probability between 5.24% and 8.99%, depending on age) were advised to make an appointment with their GP to discuss potential treatment.2 The GP was also informed about the screening result.
The Danish community-based ROSE study enrolled woman aged 65–80 years and used data obtained from a self-administered questionnaire to calculate an absolute risk of fracture using FRAX®, followed by a DXA scan in women with moderate-to-high fracture risk (≥15% at 10 years).3 Unlike the SCOOP trial, there was no difference in fracture incidence between the screening and control groups in the intention-to-treat analysis, possibly because treatment decisions were based on DXA results only.3 However, another randomised large community-based Dutch study of women aged 65–90 years examined the effect of a screening program involving DXA, vertebral fracture assessment and FRAX®, and failed to show a reduction in fractures compared with usual GP care.4 However, this may have been affected by suboptimal patient participation and incomplete medication adherence.
Due to concern that the above individual studies may have been underpowered, a subsequent meta-analysis was undertaken and found a statistically significant reduction in osteoporotic fractures (HR 0.95; 95% CI: 0.89–1.00), major osteoporotic fractures (HR 0.91; 95% CI: 0.84–0.98) and hip fractures (HR 0.80; 95% CI: 0.71–0.91), but no reduction in all fractures (HR 0.95; 95% CI: 0.89–1.02).5 The pooled HR for the secondary outcome of all-cause mortality was not significant at 1.04 (95% CI: 0.95–1.14). The number needed to screen to prevent one fracture was 247 for osteoporotic fractures and 272 for hip fractures.5 This suggested that population screening might be effective in reducing osteoporotic fractures and hip fractures. Of the three recent RCTs using FRAX®,2–4 only the SCOOP study has published a cost-effectiveness analysis, which found that a widespread community-based screening program of fracture risk in older UK woman was likely to be cost-effective.15 Widespread applicability to the Australian population remains to be determined, mainly due to the lack of an Australian-specific treatment threshold above which bone-protective pharmacotherapy should be commenced. However, a population fracture risk screening program based around the FRAX® tool and DXA appears promising.16