Rev Osteoporos Metab Miner. 2018; 10 (1) Supplement: 5-8
2 Grupo de Investigación GREMPAL – IDIAP Jordi Gol – Universitat Autònoma de Barcelona (España)
3 CIBER Fragilidad y Envejecimiento Saludable (CIBERFES) – Instituto de Salud Carlos III (ISCIII) (España)
Osteoporosis is a metabolic bone disease characterized by a low bone mass and a deterioration of the microstructure of the bone tissue that leads to an increase in bone fragility and consequently to an increased risk of fracture1. Its real incidence is difficult to calculate since it is a silent process until the appearance of the fracture. It is one of the most prevalent osteo-articular diseases in primary care consultations. Since in 1994 the World Health Organization defined the densitometric values of osteoporosis which have been widely used to identify the population susceptible to suffering a fragility fracture2. Currently, population screening strategies3 are not recommended to identify patients with osteoporosis. Rather, a precautionary search is suggested in those subjects with a high risk of fracture4. In addition, in recent years the role of the exclusive assessment of bone mass to estimate the risk of fracture in patients has been questioned. Identifying these patients at risk to direct the necessary diagnostic and therapeutic options is one of our most difficult and controversial tasks.
Risk factors for fracture
One of the first steps is to ascertain the risk factors associated with the appearance of fractures. Classically they are divided into5:
– Older: those who present a relative risk twice or more higher than the population without risk factor. We can distinguish:
1. Age >65 years. With age, the risk of fractures increases, independently of other risk factors. For every decade the risk of fracture is multiplied by 1.5-2 times.
2. Personal history of fragility fracture.
3. Family history of hip fracture, particularly in the parents.
4. Body mass index lower than 19 Kg/m2 or if there is a weight loss greater than 10% of adult weight.
5. Use of oral glucocorticoids (dose of 5 mg or more of prednisone, or equivalent, for three or more months).
6. Untreated primary ovarian failure or hypogonadism in man.
7. Frequent falls (two or more falls per year).
8. Other diseases such as hyperparathyroidism, eating disorders, chronic malnutrition and malabsorption disorders.
– Minors: those who present a relative risk between one and two times higher than the population without the risk factor. Among them are5:
1. Female sex.
3. Alcohol consumption of 3 or more basic units per day is associated with an increased risk of fracture.
4. Early menopause (before age 40).
5. Rheumatoid arthritis.
6. Type 1 diabetes is associated with a decrease in bone mass and an increased risk of fractures of any location.
7. Hyperthyroidism not corrected
In addition to these classic factors, the list of diseases (chronic liver disease, chronic renal failure, hypertension, diabetes mellitus type 2, etc.) and drugs (aromatase inhibitors, proton pump inhibitors and anticonvulsants, among others) associated with an increase in osteoporotic fracture risk has increased in recent years.
Assessment of fracture risk
Different primary care studies emphasize that in a high percentage of clinical records the risk factors are not correctly recorded6, and when they are recorded they are not taken into account when requesting a densitometry7.
We can assess the risk through a qualitative assessment (based on the number of risk factors present) or quantitative (through the use of fracture risk scales).
The 2010 National Health System guide5 recommends a qualitative assessment and, in the case of two or more major risk factors, carry out a study of bone mass.
Different national and international clinical practice guidelines consider that the presence of a previous vertebral or hip fracture, or the presence of two or more fractures from other locations, are indicators of a high risk of fracture and, consequently, they are patients that must be treated8-10.
In case of choosing to make a quantitative assessment, we have different scales: Index Fracture11, Garvan12,13, QFracture©14 and FRAX©15.
In a survey of primary care physicians in the Canary Islands, more than 75% of the physicians surveyed answered a qualitative assessment, based on the presence of risk factors, while 28.6% used risk scales regularly16.
Use of risk scales
FRAX© is the most applicable scale. It allows us to estimate the absolute risk of fracture at 10 years through a quick and simple assessment of a few risk factors. Allows calculation with or without value of bone mass. One of the main drawbacks is that many variables are dichotomous, so that it does not consider, for example, the total number and location of previous fractures or the total cumulative dose of corticosteroids. Studies conducted in cohorts of Spanish patients observe that the FRAX© tool underestimates the risk of fractures, especially for major fractures17,18.
Two calibrations of the FRAX© tool have been published for the Spanish population (Figure 1). The first of these19 proposes as low risk a risk of major fractures of less than 3.6% and as a high risk >10%. The threshold sensitivity of 3.6% for diagnosing osteoporosis was 51%, the specificity 68%, the positive predictive value 20% and the negative predictive value 90%. The other calibration comes from the FRIDEX cohort20. This considers a risk of major fractures lower than 5% and high risk if >7.5% at risk. For these cut-off points the sensitivity is 40.8%, the specificity is 92.3%, the positive predictive value is 25.3% and the negative predictive value is 96%. Its discriminative capacity is similar to the exclusive assessment of the value of the bone mass, especially for femur fracture21. These cut-offs have been validated in an external cohort22, although the low number of fractures observed and the fact that no data are available on what happens in patients at intermediate risk requires further studies.
Recent work done in 361 patients found that the predictive capacity of both cut points was similar to the qualitative assessment (presence of 2 or more major risk factors), with better values observed for the cutoff point >3.5% for the cut-off point ≥5%, when identifying high-risk patients against whom to request densitometry23.
Although at international level different clinical practice guidelines recommend the assessment of fracture risk using FRAX©8, at the national level there are few clinical practice guidelines that recommend its use when deciding which patients to direct diagnostic and therapeutic strategies, being the usual the non-recommendation of the Spanish version of FRAX©24.
The Garvan scale only considers a low number of variables (age, sex, weight, number of previous fractures, number of previous falls and bone mineral density optionally). It has been validated for a sample of 121 Spanish patients; a cut-off point >18.5% had a sensitivity and specificity of 67%25. Further studies are needed to corroborate the predictive capacity of this cut-off point for the Spanish population.
QFracture© is a scale based on the database of primary care physicians in the United Kingdom. For its calculation, 25 variables are necessary, among them the previous falls (very important predictor of fractures) and new emerging risk factors. There is no published work that validates this scale for the Spanish population.
Osteoporosis is therefore a reason for consultation that is highly prevalent in primary care. Identification and assessment are required in those patients that present a high risk of fracture based on the presence of risk factors. Although we have different scales that provide information on the absolute risk of fractures, it is not advisable to use them for the Spanish population due to the limitations mentioned above. It would perhaps be more interesting to have a scale that would allow estimating the absolute risk for the Spanish population.
Conflict of interests: The author declares that he has no conflicts of interest.
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