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Osteoporosis: the emperor has no clothes.

Järvinen TL, Michaëlsson K, Aspenberg P, Sievänen H - J. Intern. Med. (2015)

Bottom Line: However, all these three notions can be disputed.A high likelihood of falling, in turn, is attributable to an ageing-related decline in physical functioning and general frailty.There are also considerable uncertainties related to the efficacy of drug therapy in preventing clinical vertebral fractures, whereas the efficacy for preventing other fractures (relative risk reductions of 20-25%) remains moderate, particularly in terms of the low absolute risk reduction in fractures with this treatment.

View Article: PubMed Central - PubMed

Affiliation: Department of Orthopaedics and Traumatology, University of Helsinki and Helsinki University Central Hospital, Helsinki, Finland.

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Inherent inaccuracy related to dual-energy X-ray absorptiometry (DXA)-derived bone mineral density (BMD) seriously undermines the method. (a) The three body components of bone mineral, fat and lean soft tissue have different attenuation coefficients, but DXA employs two photon energies and can thus only resolve two components at a time. Therefore, assumptions are made with DXA about fat versus lean tissue ratios in the calculation of BMD. Numerous studies (using both phantoms and cadaver specimens) have consistently shown that the magnitude of uncertainty inherent in BMD measurement can be ±1 T-score. (b) To illustrate the difference between repeatability (precision error) and accuracy (error), the black cross shows a patient's result plotted on a typical DXA scan report. The blue error bars denote the same T-score result drawn with an error bar indicating the 95% confidence interval (CI) of ±0.2 in the T-score assessment arising from BMD precision errors. Finally, the same result is drawn with an error bar indicating the 95% CI of ±1.0 in the T-score assessment arising when accuracy errors and precision errors are combined. Adapted from [49].
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fig03: Inherent inaccuracy related to dual-energy X-ray absorptiometry (DXA)-derived bone mineral density (BMD) seriously undermines the method. (a) The three body components of bone mineral, fat and lean soft tissue have different attenuation coefficients, but DXA employs two photon energies and can thus only resolve two components at a time. Therefore, assumptions are made with DXA about fat versus lean tissue ratios in the calculation of BMD. Numerous studies (using both phantoms and cadaver specimens) have consistently shown that the magnitude of uncertainty inherent in BMD measurement can be ±1 T-score. (b) To illustrate the difference between repeatability (precision error) and accuracy (error), the black cross shows a patient's result plotted on a typical DXA scan report. The blue error bars denote the same T-score result drawn with an error bar indicating the 95% confidence interval (CI) of ±0.2 in the T-score assessment arising from BMD precision errors. Finally, the same result is drawn with an error bar indicating the 95% CI of ±1.0 in the T-score assessment arising when accuracy errors and precision errors are combined. Adapted from [49].

Mentions: Further, the DXA measurement inherently assumes that the scanned body region (e.g. hip or lumbar spine) comprises only bone and homogeneous soft tissue components, but it is clear that this two-component simplification conflicts with clinical reality (individual anatomy and body composition), resulting in substantial inaccuracy of individual measurement (Fig.3a). Despite the fact that DXA measurements are highly repeatable, the measurement accuracy is important with regard to estimated bone strength. The inherent uncertainty in the BMD measurement can correspond to one T-score unit to either direction or even more [48–50]. For example, a measured T-score of −2.5 (indicating osteoporosis) can reflect a true T-score of between −3.5 (clear osteoporosis) and −1.5 (slight osteopenia) without any possibility of knowing the true value for the given individual (Fig.3b). Therefore, even large individual changes in BMD, corresponding to those typically observed in clinical trials, may become irrelevant in terms of fracture prediction [51].


Osteoporosis: the emperor has no clothes.

Järvinen TL, Michaëlsson K, Aspenberg P, Sievänen H - J. Intern. Med. (2015)

Inherent inaccuracy related to dual-energy X-ray absorptiometry (DXA)-derived bone mineral density (BMD) seriously undermines the method. (a) The three body components of bone mineral, fat and lean soft tissue have different attenuation coefficients, but DXA employs two photon energies and can thus only resolve two components at a time. Therefore, assumptions are made with DXA about fat versus lean tissue ratios in the calculation of BMD. Numerous studies (using both phantoms and cadaver specimens) have consistently shown that the magnitude of uncertainty inherent in BMD measurement can be ±1 T-score. (b) To illustrate the difference between repeatability (precision error) and accuracy (error), the black cross shows a patient's result plotted on a typical DXA scan report. The blue error bars denote the same T-score result drawn with an error bar indicating the 95% confidence interval (CI) of ±0.2 in the T-score assessment arising from BMD precision errors. Finally, the same result is drawn with an error bar indicating the 95% CI of ±1.0 in the T-score assessment arising when accuracy errors and precision errors are combined. Adapted from [49].
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4497616&req=5

fig03: Inherent inaccuracy related to dual-energy X-ray absorptiometry (DXA)-derived bone mineral density (BMD) seriously undermines the method. (a) The three body components of bone mineral, fat and lean soft tissue have different attenuation coefficients, but DXA employs two photon energies and can thus only resolve two components at a time. Therefore, assumptions are made with DXA about fat versus lean tissue ratios in the calculation of BMD. Numerous studies (using both phantoms and cadaver specimens) have consistently shown that the magnitude of uncertainty inherent in BMD measurement can be ±1 T-score. (b) To illustrate the difference between repeatability (precision error) and accuracy (error), the black cross shows a patient's result plotted on a typical DXA scan report. The blue error bars denote the same T-score result drawn with an error bar indicating the 95% confidence interval (CI) of ±0.2 in the T-score assessment arising from BMD precision errors. Finally, the same result is drawn with an error bar indicating the 95% CI of ±1.0 in the T-score assessment arising when accuracy errors and precision errors are combined. Adapted from [49].
Mentions: Further, the DXA measurement inherently assumes that the scanned body region (e.g. hip or lumbar spine) comprises only bone and homogeneous soft tissue components, but it is clear that this two-component simplification conflicts with clinical reality (individual anatomy and body composition), resulting in substantial inaccuracy of individual measurement (Fig.3a). Despite the fact that DXA measurements are highly repeatable, the measurement accuracy is important with regard to estimated bone strength. The inherent uncertainty in the BMD measurement can correspond to one T-score unit to either direction or even more [48–50]. For example, a measured T-score of −2.5 (indicating osteoporosis) can reflect a true T-score of between −3.5 (clear osteoporosis) and −1.5 (slight osteopenia) without any possibility of knowing the true value for the given individual (Fig.3b). Therefore, even large individual changes in BMD, corresponding to those typically observed in clinical trials, may become irrelevant in terms of fracture prediction [51].

Bottom Line: However, all these three notions can be disputed.A high likelihood of falling, in turn, is attributable to an ageing-related decline in physical functioning and general frailty.There are also considerable uncertainties related to the efficacy of drug therapy in preventing clinical vertebral fractures, whereas the efficacy for preventing other fractures (relative risk reductions of 20-25%) remains moderate, particularly in terms of the low absolute risk reduction in fractures with this treatment.

View Article: PubMed Central - PubMed

Affiliation: Department of Orthopaedics and Traumatology, University of Helsinki and Helsinki University Central Hospital, Helsinki, Finland.

Show MeSH
Related in: MedlinePlus