Commentary by Judith Brenner MD, Associate Editor, Clinical Correlations. Reviewed by Valerie Peck MD, NYU Division of Endocrinology.
An 81 year old Caucasian woman with a history of diabetes and hypertension who was admitted to the orthopedic service with a hip fracture after falling in her home.
This is a typical story and represents the end stages of osteoporosis. It is the myocardial infarction of the bone world. Like cardiovascular disease, prevention and identification of at-risk individuals is the most powerful tool clinicians have available to make an impact and prevent outcomes such as these.
The questions we face are:
Who is most at risk?
When do we intervene?
What is our intervention?
So, how do we quantify risk?
Up until now, it has essentially been the results of bone mineral density testing that’s guided us as to whether or not to offer therapy. In those patients with osteoporosis (defined as a T score <-2.5), the answer is simple: treat. Patients with “osteopenia” (defined as T score -1.0 to -2.5), however, are a much larger group and the answer about treatment is not always clear. In order to identify those most likely to benefit, we need to rely on risk factor assessments, much like we do when we decide to initiate statin therapy for hyperlipidemia. Clearly those at highest risk to fracture are more likely to benefit from intervention. If we could translate their combined risks into a number the way Framingham does for cardiovascular risk assessment, clinicians could target their interventions to the individuals that would truly benefit. A brand new tool, called FRAX does just this.
The World Health Organization, led by Dr. John Kanis, created this tool to calculate two numbers:
a patient’s 10 year probability of having specifically a hip fracture
a patient’s 10 year probability of sustaining any major osteoporotic fracture
The risk factors included in this tool are:
-Sex (men get osteoporosis too, manifesting later in life because of higher peak bone mass plus the benefit of not incurring the rapid bone loss associated with menopause)
-Weight and height (related to loading forces which stimulate osteoblasts in a patient with greater body mass)
-Previous fracture (this identifies patients who already have osteoporosis)
-Parent with a fractured hip (the value of family history)
-Secondary osteoporosis (e.g. vitamin D deficiency, hyperparathyroidism)
-Alcohol (>3 drinks a day)
Importantly, FRAX does NOT hinge on the result of bone mineral density testing. When using the on-line tool, you can enter results of BMD of the femoral neck; however, if the information is not available to you, it’s been found that risk can be calculated with bmi and clinical risk factors. Another huge advance of FRAX is in allowing clinicians to quantify risk in groups we previously have not had adequate information on, namely men and non-Caucasian white women. Since the majority of studies on osteoporosis have been done on Caucasian women, up until now, it was unclear if this data could be used in other groups. In the development of this tool, WHO undertook a mammoth effort and evaluated epidemiologic and cost effectiveness data throughout the world.
To illustrate the power of this tool, consider the following:
Your patient is a 60 year old woman, 110 lbs, 5 ft tall, with no family history or personal history or fracture, no history of smoking or use of steroids.
Using the FRAX tool, hr 10-year risk of hip fracture is: 1.5%.
If we made that patient 200 lbs, her risk would be 0.5%.
If we gave that same 110 lbs patient a history of a parent with an osteoporotic fracture, her risk would rise to 1.9%.
Now add to that a personal history of smoking. Her risk rises to: 2.85%.
Did I mention that she’s had IBD and has been treated over the years with low doses of glucocorticoids? Her risk now rises to 5.9%
Lastly, she drinks every night. Now this patient’s risk is: 9.0%
But notice how powerful age is as a risk factor: if we made the 60 year old woman 80 years old, 110 lbs, 5 ft tall, with no family of personal history of fractures, no history of smoking and no use of steroids, her 10-year risk of hip fracture would be 10 % in 10 years and she would have a 35% chance of the development of any “major osteoporotic” fracture.
The question then becomes, how do numbers translate to treatment? Based on a cost effectiveness analysis, the magic number is a 3% risk of hip fracture in 10 years or 20% risk of any other major osteoporotic facture. For most, the treatment of choice is a bisphosphonate with 1500 mg of elemental calcium and 1000 IU of vitamin D and regular weight-bearing exercise. Though the data behind calcium and vitamin D supplementation is beyond the scope of this post, note that the current recommendation of 800IU of vitamin D is being increased to 1000 IU a day.
For an in depth review of osteoporosis management, refer to www.nof.org. A clinician’s guide can be downloaded at no cost.
Bottom lines about FRAX:
FRAX is a simple to use, online risk calculator that allows clinicians to quantify the risk of developing a hip or other osteoporotic fractures over 10 years and can be used in patients in the 50-70 year old age range
FRAX does not only rely on bone mineral density testing
FRAX allows the accurate quantification of risk in non- Caucasian women and in men
Dawson-Hughes B et al. Implication of absolute fracture risk assessment for osteoporosis practice guidelines in the USA. Osteoporosis Int (2008): 19;449-58.
Khosta, S et al. Osteopenia. New England Journal of Medicine 2007; 356(22):2293-2300.
Siris, E, Delmas, P.D. Assessment of 10-year absolute fracture risk: a new paradigm with worldwide application. Osteoporosis Int (2008): 19;383-84.
Clinician’s Guide to Prevention and Treatment of Osteoporosis on www.NOF.org