Reporting fracture risk

The previous discussion highlights the clinical dilemma of the densitometrist in explaining what these numbers mean, because the level of bone density that constitutes a diagnosis of osteoporosis is not necessarily the same level of bone density that constitutes an unacceptable level of risk for fracture. The prediction of fracture risk is therefore a separate statement.

It is not clear why the Canadian Panel chose to emphasize reporting qualitative assessments of fracture risk instead of quantitative assessments. Nevertheless, for the referring physician, the overriding issue may certainly be whether the patient is at increased risk of fracture or not. The exact magnitude of any increase in risk may be less important. There is no agreement as yet as to the ideal form that a quantitative assessment of fracture risk should take. There are certainly a growing number of quantitative assessments from which to choose. Relative risk data, whether used with the T-score or z-score is poorly understood and not particularly useful clinically. Instead, global or site-specific fracture risk predictions such as RLFP, 10-year, or lifetime fracture risks are both intuitive and useful.2 The presence of a fracture and/or multiple clinical risk factors can be combined into a quantitative assessment of risk or they can simply be noted to increase the risk beyond the stated projections. The overriding goal in any of these approaches is to ensure that the magnitude of the risk is recognized so that appropriate interventions are recommended. Typical statements, depending on the modality chosen for expressing fracture risk for a 60-year-old postmenopausal woman with a femoral neck T-score of -2.0 are as follows:

The patient's RLFP or the number of osteoporotic fractures she is expected to experience in her lifetime is 5.48. The patient's lifetime risk of hip fracture is 27%.

The patient's 10-year probability of having any type of osteoporotic fracture is 13%.

As noted in the study from Fuleihan et al. (3), many densitometry centers do not employ any age restriction on fracture risk predictions. This is inappropriate. Such pre

1 See Chapter 9 for a discussion of the 1991 and 1993 Consensus Conferences' definition of osteoporosis.

2 See Chapter 10 for a discussion of these methods for predicting fracture risk.

dictions should be reserved for women age 60 and older and probably for men of the same age as well. This is the age group in which the relationship between bone density and fracture risk has been studied. Fracture risk predictions should not be made in otherwise healthy young adults because there is no data to support doing so. It is also clear that for any given level of bone density, the risk of fracture is markedly less in these individuals than in older individuals.

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Essentials of Human Physiology

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