Polish Foundation of Osteoporosis

STANDARDS

• Our Duty
• Fracture Risk Calculator

What is Our Duty: Diagnosing Osteoporosis or Fracture Risk Assessment?

Should we focus on the traditional, although gradually changing, approach to osteoporosis, or perhaps we had better concentrate on diagnosis and treatment /preventing the first or subsequent fracture? To answer the question a doctor needs to opt for one of two alternatives. Following first option means diagnosing the disease according to the official definition. Choosing the other requires fracture risk evaluation, regardless of the cause of fracture, and thus not only osteoporosis-related fracture.

Each and every element of either option is characterized by some relativism allowing to choose (and support) any of them (e.g. BMD) as the aim of diagnosis and treatment. Still, a single term of osteoporosis is invariably used. So what is osteoporosis? Osteo-bone, porosis-of porous condition, hence osteoporosis is the thinning of bone tissue / loss of bone density. 65 years ago Albright accurately defined it as „too little bone in the bone”. It seems to be a natural process in an aging bone. All tissues undergo age-related changes. They manifest themselves in grey hair, fragile blood vessels, slack skin and flabby muscles, decreased efficiency of sensory organs, and in the locomotor system – poorer skills in overcoming everyday obstacles which makes the patient more susceptible to falling. The volume of bone, its mass and strength decline, its quantity and quality suffer, and the risk of fracture increases.

And so, the mean absolute 10-year risk of hip fracture in European women does not exceed 0,5% in the 6th decade of life, 1,6% in the 7th decade, 5,3% in the 8th decade, and above the age of 80 the value reaches 12,3% (1). These numbers apply to the whole population, comprise all osseous and non-osseous aspects, are based on prospective studies and are known as population risk. In the age group of 60-69 one in every 62 women will suffer a hip fracture. In the next decade one woman in 18 (5,3%), and above the age of 80-every one in eight women. Because the number of 80 or more year-old women is several times lower than 60 and 70-year-olds, the number of fractures is at its highest among the younger and more numerous population. (2)

The traditional view on osteoporosis depends on four corresponding and simultaneous elements:

• with advancing age
• the percentage of older population falls down
• BMD/bone mass decreases and
• the frequency of fractures rise.

At this stage a question arises whether accordingly viewed osteoporosis should be recognize as a condition or a symptom of bone aging? As in every individual case the intensity of the process depends on epidemiologically identified factors such as genetic predisposition, lifestyle and eating habits, other accompanying conditions or drugs which all have negative impact on bone tissue.

The 1994 WHO Standards for Osteoporosis defined it as a condition characterized by low bone mass and disturbed bone microarchitecture.(3) In order to meet the criteria of the definition we need to know the exact borderline between a healthy and diseased bone.

It was a common practice in establishing the norm for BMD to consider BMD lower than 2 Standard Deviations as pathologically low. Later modifications divided T-score (the curve of bone mass falling with age) into normal, osteopenia and osteoporosis. In later practice, T-score of -2.5 became the threshold for diagnosing osteoporosis. Thus defined borderline between the healthy and those suffering from osteoporosis was based on BMD test results only. The consequences of such a division meant that persons with correct or osteopenic BMD were denied medical treatment.

However, research into fracture epidemiology in the last several years, which compare low-energy fractures against BMD, has shown that between 55% and 75% of such fractures affect persons with BMD between normal and osteopenic (4, 5, 6), with T-score around -1.5. That is persons, who – according to the WHO definition – do not have osteoporosis! The number of fractures is considerably higher in people with factors other than low BMD. Only in a substantially smaller group of the oldest population osteoporosis may be the cause of fracture.

At this stage we need to consider the essence as well as the source of bone susceptibility to low-energy fractures. That in turn requires re-defining of our - doctors' responsibility toward the patient. The responsibility is to estimate rather not the risk of osteoporosis but first and fore mostly the risk of fracture, whatever its cause is.

At the NIH Conference in 2000 osteoporosis was defined as a skeletal disorder characterized by compromised bone strength reflecting its quality and quantity deficiency.(7)

General as it has to be, the definition illustrates present-day knowledge (or rather helplessness) and offers new possibilities of diagnosing osteoporosis. We have no tool capable of evaluating all the elements determining bone strength or the threshold of resistance to fracture, for instance resulting from a minor trauma such as a fall from own height. Using the most general terms, with the vagueness they carry, we define osteoporotic fracture to be a low-energy fracture, one which will bear no consequences for the majority of people. Osteoporosis can not be diagnosed before this low energy fracture occurs. Just as myocardial infarction can not be recognized until it happens.

Even being fully equipped with the knowledge of bone quality we are unable to assess the risk of fracture without taking into account the influence of extra-osseous factors. Example: there are two patients with identical bone condition. One of them suffered fracture due to a fall. In this particular case osteoporosis was diagnosed only because of the involvement of an absolutely non-osseous factor. Clearly, bone tissue examination is only one of several steps leading to the recognition of fracture risk.

Bearing that in mind, what tools do we have to assess fracture risk? It is helpful to use epidemiological data on the fracture risk factors (FRF), which make it possible to calculate how much Relative Risk (RR) of such FRF increases risk of fracture in examined patients compared to population risk. For example, as in the case of myocardial infarction (MI) how much is the risk of MI higher in patients with diabetes, high blood pressure, obesity, dyslipidemia, or smoking? Or, as in the case of osteoporosis, how much fracture risk is higher in a person with a history of low-energy fracture, who smokes and has undergone a therapy with glycocorticosteroids?

A database has been created by a WHO working group with all epidemiological studies carried out under the same medical standards.(8) They identified independent risk factors. This independence means that operating independently such a factor increases the risk of fracture as compared to population risk. Obviously the more factors operate at the same time the greater the risk.

The methodology of 10 year evaluation (10 year accepted as the optimal period) of absolute individual risk of fracture (AR-10) of the hip is presented in AR-10 Calculator. It helps to evaluate the risk of fracture in every person, at every age and includes all known independent factors (low BMD with Z-score below 0.0 being one of them) affecting the examined patient or population group.

We strongly advocate for the evaluation of individual, absolute, 10-year fracture risk of the hip as the diagnostic aim which determines the intervention threshold. And we define osteoporosis as high fracture risk.

Source data:

1. Kanis JA. et co.: Assessment of fracture risk. Osteoporos Int 2005, 16;6:581.
2. Siris E. et co.: Identification and Fracture Outcomes of Undiagnosed Low Bone Mineral Density in Postmenopausal Women. JAMA. 2001, 286:2775.
3. World Health Organization. Assessment of fracture risk and its application to screening for postmenopausal osteoporosis. Technical Report Series 843;WHO, Geneva 1994.
4. Burger H. et co.: Risk factors for increased bone loss in an elderly population: the Rotterdam Study. Am J Epidemiol 2000, 9; 147:871.
5. Wainwright SA. et co.: Hip Fracture in Women without Osteoporosis. J Clin . Endocrinol. Metab. 2005, 90:2787.
6. Nowak NA. i wsp.: Epidemiologia osteoporozy u kobiet w aglomeracji Bia³egostoku (BOS), I: Gêstoœæ koœci a z³amania. Postêpy Osteoartrologii 2003, 14:1.
7. Osteoporosis Prevention, Diagnosis, and Therapy NIH Consensus Development Panel on Osteoporosis Prevention, Diagnosis and Therapy. JAMA 2001, 285; 6:785.
8. Kanis JA. WHO criteria for indications to treatment. Osteoporosis Int 2006, 17:S1.