The World Health Organization (WHO) defines osteoporosis as a skeletal disorder characterized
by low bone mass combined with microarchitetural deterioration of the bone, leading
to bone fragility and increased susceptibility to fracture. Its clinical relevance
relies on the emerging fracture rate, as well as on the morbidity and mortality associated
with hip fractures. Moreover, the WHO objectively defines osteoporosis based on bone
mineral density (BMD, [that is, when BMD is ≤ -2.5 standard deviations [SD] below
peak bone mass [T-score], as assessed by dual X-ray absorptiometry [DXA]). A T-score
between -1.0 and -2.5 means an intermediary condition of bone loss, which is called
osteopenia. There is no doubt that the risk of fracture increases significantly with
decreasing BMD. In spite of this, it is well known that osteoporotic fractures occur
across a wide spectrum of BMD intensity. Actually, the much larger number of persons
with osteopenia determines a significant occurrence of fractures in people diagnosed
with this condition. There is no global consensus for screening patients at risk of
osteoporotic fracture; however, several medical associations recommend a targeted
approach to the prevention of osteoporosis based on the 10-year absolute risk of osteoporotic
fracture.
The main purpose of the treatments for osteoporosis is to decrease the risk of fragility
fractures. Therefore, the capacity to assess the risk of fracture is critical for
the identification of patients who are eligible for intervention.[1] The fracture risk assessment tool (FRAX), a computer based algorithm, is the most
thoroughly studied and widely used tool to calculate the risk of fracture.[2] The FRAX was released in 2007 by the World Health Organization Collaborating Centre
at Sheffield, United Kingdom (UK), to estimate the individualized 10-year probability
of hip and major osteoporotic fractures (hip, clinical spine, distal forearm, and
proximal humerus).[3] The FRAX tool integrates 8 clinical risk factors (CRFs): previous fragility fracture,
parental hip fracture, smoking, systemic glucocorticoid use, excess alcohol intake,
body mass index, rheumatoid arthritis, and other causes of secondary osteoporosis);
those, in addition to age, sex and BMD at the femoral neck (an optional input) contribute
to the 10-year fracture risk estimate. The probability of fracture is computed taking
the risk of fracture and the risk of death into account.[3]
The FRAX is increasingly being used as a guide for clinical decision-making, and FRAX
models are currently available for 63 countries and in 32 languages, covering 79%
of the world population aged 50 years or older.[4] As fracture probability differs markedly within and across regions of the world,[5] the existing FRAX models were calibrated to the epidemiology of fracture and death
in individual nations. The FRAX model for Brazil was released in 2013, and in 2015
an important paper was published, and it described the data used to develop and calibrate
the Brazilian FRAX model, illustrating its features and developing intervention thresholds.[6] The FRAX tool is the first to provide a country-specific fracture-prediction model
for Brazil, and it was recently integrated into the Brazilian guidelines for the diagnosis
and treatment of postmenopausal osteoporosis,[7] adopting the approach recommended by the National Osteoporosis Guideline Group (NOGG)
in the UK, in which the intervention threshold is set at the age-specific fracture
probability equivalent to women with a previous fragility fracture.[8] The NOGG management strategy requires the consideration of two additional thresholds:
the lower assessment threshold (a probability below which neither treatment nor a
BMD test should be considered), and the upper assessment threshold (a probability
above which treatment may be recommended irrespective of BMD). Those with probabilities
above the lower assessment threshold but below the upper assessment threshold should
be considered for a BMD test and have their fracture probability reassessed.[8]
Since the release of the FRAX Brazil in 2013, there have been questions related to
the limitation of the epidemiological studies that served as database for its calibration,
as well as questions regarding whether or not those facts could diminish the relevance
of the Brazilian FRAX tool in the clinical practice. Information about the epidemiology
of fractures in Brazil is sparse.[9] There are, however, several published regional reports on the incidence of hip fracture
in different regions of Brazil.[10]
[11]
[12]
[13] Briefly, the calibration of the FRAX Brazil was performed using data from four Brazilian
epidemiologic studies, and, as there was no consistent difference in hip fracture
incidence according to region, the results were amalgamated to obtain a national data
estimate on the incidence of hip fracture and mortality.[10]
[11]
[12]
[13] Those studies have been conducted in the cities of Porto Alegre (located in Southern
Brazil),[13] Marília (located in the Southeast[12]), and Sobral[10] and Fortaleza[11] (located in the Northeastern region of the country). While recognizing that the
estimates of data on hip fracture rates representing the whole country were based
on regional studies, there was no consistent difference in the results among the studies,
all of which followed a robust methodology and were published in peer-reviewed international
journals, and their combined results were considered representative of the epidemiology
of hip fractures in Brazil by the original FRAX developers.[6] Another frequent question refers to the fact that Brazil is a multiethnic country,
and fracture rates may differ according to ethnicity. In the vast majority of available
FRAX models worldwide, ethnicity could not be built into the models due to the paucity
of data from which to populate any model. In fact, fracture probabilities based on
ethnicity are only present in the FRAX USA and FRAX Singapore.[6] In Brazil, the regional estimates included those from the Northeastern, Southern
and Southeastern regions, which have populations of mixed ethnicity, and, again, there
was no consistent difference in the incidence of hip fracture according to region,
suggesting that the decision to amalgamate the regional data was reasonable.[6]
In summary, the FRAX Brazil is a free online tool that helps Brazilian clinicians
to better identify women and men in need of intervention (at the highest risk of fragility
fracture), and, thereby, it helps improve the allocation of our limited healthcare
resources. The FRAX Brazil utilizes several known clinical risk factors rather than
BMD alone to calculate a patient's 10-year fracture probability, thus making it particularly
useful in parts of our country where the DXA technology is scarce or not available.
Moreover, the tool is calibrated by the best available epidemiological data in our
country, and can be continually upgraded as new data emerge, ensuring greater efficiency
and ease-of-use in the clinical practice.
