National Osteoporosis Foundation (NOF) / International Society for Clinical Densitometry (ISCD) FRAX Implementation Guide
The International Society for Clinical Densitometry (ISCD) and the National Osteoporosis Foundation (NOF) recognize the importance of, and intense interest surrounding, the fracture probability assessment tool, FRAX®. The NOF and ISCD have developed a FRAX filter to assist US physicians in utilizing FRAX and the NOF guidelines when manufacturers release FRAX as part of the DXA report. The NOF and ISCD have recommended that these guidelines be incorporated into the reporting software. The following links take you to the full guideline text and a PDF copy of the guideline. NOTE: These recommendations apply only to the US. (9.16.09)
Fracture Risk Models in Clinical Practice
The key to addressing the impact of osteoporosis and is to identify patients at risk of the disease prior to fracture and to ensure that these patients are appropriately screened and treated if necessary. DXA can be used to diagnose osteoporosis1-3. However, it can also be used to predict fracture risk4-10, since the risk of fracture increases as BMD decreases in men and women6. Low BMD is the single best predictor of future fracture in postmenopausal women without prior fracture3,10 and has similar predictive potential in elderly men9. Fractures are multifactorial in origin2-4,7-10, however, so identifying persons at greater risk involve direct patient assessment using knowledge of risk factors for fractures and falls. Persons with multiple risk factors for fracture are at much higher risk of future fracture than persons with any single risk factor, including low BMD7-10. Combining BMD with other risk factors such as age or prior fracture, or combining multiple risk factors greatly enhances the ability to predict persons or populations at increased risk for future fractures7-10. This is important since many persons who fracture do not have osteoporosis by DXA criteria10,11. Independent predictors of future fracture identified from multiple studies include prior fracture, low BMD, fall, advancing age, glucocorticoid use and frailty4,6-12. Fracture risk tools have thus been developed which may assist clinicians to identify groups of patients, or individuals, at increased risk of fracture13-15. By considering multiple risk factors when assessing fracture risk, rather than just BMD, the number of persons needing treatment to prevent a single fracture could be dramatically reduced from several thousand to less than one hundred16.
Risk factors have limitations for assessing risk and prognosis17-19 highlighting the difficulties involved in trying to achieve effective risk stratification in multifactorial disease processes such as osteoporosis4,12. Although fracture risk models predict populations at increased risk of fracture, the result for an individual person is usually an average number around which there is usually considerable variation7,12. Although fracture risk models are interesting tools, each model has shortcomings which need to be taken into account when evaluating individual patients with their results.
Some of the short-comings of FRAX® have been identified and corrected; for instance: elimination of the Z-score from the tool and more recently substitution of the T-score with the manufacturers actual BMD. Similar to diagnostic tests, the internal and external validity, sensitivity and specificity of these models need to be considered. Although fracture risk models may have high internal validity20, recently presented results of a study evaluating the external validity of FRAX using data from the Women’s Health Initiative were disappointing showing the c-statistic to be around 0.621. While studies differ, they do suggest that risk factors for fracture differ between women of different ethnicities8, and between men and women7-9, adding complexity to the assessment of fracture risk. This has resulted in the development of different fracture risk assessment tools13-15. To facilitate ease of use, presently available risk models are parsimonious and thus no tool will incorporate all possible risk factors. Other issues concerning FRAX have already been highlighted with specific examples22, and further discussion will take place at the next ISCD Position Development Conference in 201023.
The information generated with the use of these tools may assist physicians in making decisions about who to treat, especially for patients with osteopenia. However, there are no published studies showing that any fracture model clearly supersedes a clinician’s own judgment. In addition, prior studies have shown that some elderly women have a very high 1-year risk of fracture – around 25% – thus a prediction model is not needed in such instances24. Thus fracture prediction models should be used judiciously in managing individual patients.
FRAX: Fracture Risk Assessment tool.