Risk Score Predicts Fracture for Osteoporotic Women

MELBOURNE, Australia, Sept. 26 -- A fracture risk score for osteoporotic women may help clinicians decide how to proceed when multiple-site bone mineral density measurements disagree, researchers said.

The score successfully predicted 75% of fractures that occurred over two years of follow-up with 68% specificity, said Margaret Joy Henry, BSc, Ph.D., of the University of Melbourne in the October issue of Radiology.

While bone mineral density is commonly measured at both the spine and hip, there is little available guidance for treatment decisions when these measurements conflict -- as they did in 44% of controls and 48% of fracture cases in the study.

Notably, the investigators reported increasing fracture risk with increasing body weight after adjustment for bone mineral density, which may be due to increased force applied to the skeleton during a fall. Previous studies have indicated higher risk with lower body weight due to lower bone mass.

The following predictors of minimal trauma fracture (fractures from a fall from less than standing height, spontaneous fracture, or accidental strike against a person or object) were included in the score:

• Falls score in the previous year (1=never or rarely, 2=a few times, 3=several times, 4=regularly),
• Number of previous fractures resulting from minimal trauma since age 20 by self-report,
• Weight, and
• Bone mineral density at the spine and femoral neck.

The risk score equation used was 9.304 - 4.735 (spinal bone mineral density in grams per square centimeter) - 4.530 (femoral neck bone mineral density) + 1.127 (falls score) + 0.344 (number of previous fractures) + 0.037(weight in kg). The optimal cut point was 5.4, beyond which a woman would be expected to have a fracture.

According to the risk score, a woman with a falls score of 1, average weight, no previous fracture and a T score of 0 at the posteroanterior spine and femoral neck would have a risk score of 2.4 and therefore be predicted to be have no fracture within the next two years. On the other hand, a woman with a falls score of 4, three previous fractures, and a posteroanterior spine and femoral neck T score of 2.5 would have a risk score of 9.8 and would be clearly expected to have a subsequent fracture.

The study included 231 women 60 or older who had a minimal traumatic fracture of the hip, spine, humerus or a Colles fracture (fractures included in the World Health Organization definition of osteoporosis) in the period 1994 to 1996 on the basis of reports from two radiology practices.

Characteristics of fracture cases were compared to those of 448 controls randomly selected of women stratified to match the age profile, living in the same region, and who had not sustained a fracture within the two-year period.

To confirm the predictive ability of the risk score, it was used on another 600 women 60 or older who were followed for 5.8 years for fractures. Participants were removed from the data set after their first fracture.

Sensitivity of the fracture risk score decreased over time though specificity did not decline. The investigators said this is likely due to other unmeasured factors that increase in importance over time.

The study was limited by determining fracture cases based on radiographic reports, which were subjective and did not include vertebral heights or spinal deformity index. The spine fractures were likely underrepresented in the study cohort, the researchers said.

The equation used to calculate the fracture risk score can assist in the assessment of fracture risk, particularly among patients with discordant bone mineral densities at the spine and hip, they concluded.

Predicting fracture risk may allow for use of a variety of treatment regimens including hormone replacement therapy, non-hormonal medicines, vitamin D and calcium supplements or calcitriol.

The U.S. Preventive Services Task Force recommends that women aged 65 and older be screened routinely for osteoporosis or beginning at age 60 for women at increased risk for osteoporotic fractures.