Pam Harrison      
September 07, 2016

Age-dependent thresholds to help decide when to intervene are preferred over fixed intervention thresholds when the Fracture Risk Assessment Tool (FRAX) is used for assessment of osteoporosis, but the former must be country-specific, as the epidemiology of fractures varies widely from country to country, a new systematic global review of FRAX guidelines indicates.

"The use of FRAX is a better way to direct treatment for osteoporosis than bone-mineral density [BMD], although both are important, and once you have generated a FRAX number, how you use it is particularly important," lead author John Kanis, MD, emeritus professor in human metabolism at the University of Sheffield, United Kingdom, told Medscape Medical News.

"I wouldn't say any method is perfect, but the age-dependent threshold is a reasonable method with a reasonable rationale that appears to work well to identify individuals at high risk for fragility fracture," he added.

The review was published recently in the Archives of Osteoporosis.

FRAX Alone Comparable to BMD for Osteoporosis Assessment

FRAX is a tool developed by the World Health Organization to help primary-care physicians calculate a patient's 10-year probability of having either a hip or a major osteoporotic fracture based on clinical risk factors alone.

BMD as assessed by DEXA can be applied to the FRAX score to improve its accuracy, but the performance of FRAX without BMD has a predictive value that is comparable to the use of BMD alone, as the review authors point out.

FRAX is intended to identify fracture risk almost exclusively in patients who have not yet sustained a fracture, as in many countries patients who have already sustained a fragility fracture are automatically considered for antiosteoporosis treatment.

In their new review, Dr Kanis and colleagues reviewed 58 publications, more than half of which used a "fixed" fracture probability of 20% as an intervention threshold.

"Many also mention a hip-fracture probability of 3% as an alternative intervention threshold," Dr Kanis observed.

However, in many countries, these fixed thresholds were based solely on recommendations issued by the National Osteoporosis Foundation of the United States and were not tailored to the epidemiology of fracture risk for that specific country, he points out.

He argues that because the likelihood of any individual sustaining a fragility fracture varies greatly in different regions of the world, each country needs to determine the probability of fracture risk that is country-specific to determine at what point antiosteoporosis treatment should be recommended.

Use Age, Sex, BMI, and Other Risk Factors

A number of organizations including the US Preventative Services Task Force have recommended a fixed threshold — such as the fracture probability of 20% — for treatment intervention.

"The use of a fixed FRAX threshold has some intuitive appeal in that it directs intervention in an equitable manner and is more readily used in clinical practice than more complex approaches inherent in the application of age-dependent thresholds," Dr Kanis concedes.

On the other hand, studies have shown that age-dependent thresholds for FRAX — which were developed by the National Osteoporosis Guideline Group (NOGG) in the United Kingdom — are more effective than fixed thresholds at identifying populations at high risk for osteoporotic fracture.

The review authors thus recommend that practitioners avoid the use of a fixed FRAX intervention threshold as the main gateway to assess fracture risk.

As Dr Kanis and colleagues observe, practitioners should begin to assess patients for future fracture risk on the basis of age, sex, body mass index, and the presence or absence of clinical risk factors.

For example, "on this information alone, some patients at high risk may be considered for treatment without recourse to BMD testing," they state.

Men and women whose probability of fracture is below the lower assessment threshold can be reassured that they are at low risk for future fracture and require no treatment.

On the other hand, patients whose 10-year probability for fracture is above the lower assessment threshold — but below the upper assessment threshold — may be considered for BMD testing in order to recalibrate their fracture risk, the review authors suggest.

And both men and women with a high likelihood of sustaining either a major osteoporotic fracture or a hip fracture based on their FRAX score may be automatically considered for treatment.

Since its launch in 2008, FRAX has increasingly been used in clinical practice to assess individual fracture risk, and specific calculators are now available for 58 countries and in 32 languages athttp://www.shef.ac.uk/FRAX.

Dr Kanis has no financial interest in FRAX. Disclosures for the coauthors are listed in the article.

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Arch Osteoporos. Published online July 27, 2016.Abstract

資料來源：Medscape