Nancy A. Melville

October 23, 2012

MINNEAPOLIS, Minnesota — The Fracture Risk Assessment Tool (FRAX), recommended by the US Preventive Services Task Force (USPSTF) to identify younger postmenopausal women at risk for osteoporosis, finds substantially fewer candidates for bone mineral density (BMD) screening than 2 other common strategies, according to research presented here at the American Society for Bone and Mineral Research (ASBMR) 2012 Annual Meeting.

The USPSTF endorsed the Web-based FRAX tool in 2011 to identify women between the ages of 50 and 64 for BMD testing if their 10-year risk for a major fracture is 9.3% or greater according to the tool without BMD screening.

Prior to FRAX, however, other risk assessment tools were available. The Simple Calculated Osteoporosis Risk Estimation (SCORE) is based on age; weight; race; rheumatoid arthritis; nontraumatic hip, wrist, or rib fracture in persons older than 45 years; and prior estrogen therapy use. The Osteoporosis Self-Assessment Tool (OST) is based on weight and age.

To compare the proportion of participants who would be identified for BMD testing by each of the 3 approaches, a research team led by Carolyn Crandall, MD, of the University of California, Los Angeles, evaluated data on 5165 women between the ages of 50 and 64 who had completed questionnaires and who had had their baseline BMD measured at 3 clinical sites of the Women's Health Initiative.

The participants were selected from a larger group on the grounds of having available complete risk factor and femoral neck BMD information and on the basis of their not taking bisphosphonates, raloxifene, calcitonin, or parathyroid hormone.

The authors found that, using the USPSTF's approach (FRAX), 15.2% would have been selected for BMD testing, compared to 32% with the SCORE approach and 36.0% with the OST.

Using the definition of osteoporosis as a T-score of -2.5 or lower, only 34% of women would be recommended for BMD testing using FRAX, compared to as many as 74% with SCORE and 80% with OST.

Adjusting for baseline hormone therapy did not affect the results.

Interestingly, the specificity for FRAX in identifying T-scores of less than -2.5 was higher (86%) than SCORE (71%) and OST (66%).

Higher Specificity Seen

"The specificity is much higher for FRAX than the other tools in identifying women with a femoral T-score of less than or equal to -2.5," Dr. Crandall said. "The pattern was especially pronounced in younger women, aged 50 to 54, and not as much in the older women."

She noted that the results nevertheless highlight striking differences between the 3 tools.

"Among US women aged 50 to 64 in our sample, the proportion with T-scores less than or equal to -2.5 identified was one third using USPSTF strategy, three quarters using SCORE strategy, and four fifths using OST strategy. However, the FRAX strategy had the highest specificity."

"Because the goal of osteoporosis screening is to identify postmenopausal women with BMD T-scores of less than or equal to -2.5 for pharmacologic therapy, we feel our results could have substantial implications for osteoporosis screening of younger postmenopausal women in clinical practice."

Bone specialist Michael McClung, MD, founding director of the Oregon Osteoporosis Center, in Portland, said that the results were not surprising, however, due to the design differences between the 3 assessment tools.

"FRAX was not designed to be a predictor of BMD, while SCORE and OST were," he said. "FRAX was developed to combine BMD and clinical risk factors to do a better job of segregating individuals into categories of high, medium, and low risk for fracture," Dr. McClung explained.

"If FRAX had been a good predictor of BMD, it would be no better than BMD in predicting fracture risk — so these results are exactly what one would expect from FRAX and the other tests, given their reason for development and validation of their effectiveness."

The tool has a somewhat different function and value for clinicians, he noted.

"The main strength of FRAX is that it is an accurate predictor of fracture risk in healthy postmenopausal women and older men — and answers the question that perplexed clinicians before its availability — 'which patients who do not have osteoporosis should receive drug treatment for osteoporosis?' " Dr. McClung said.

Dr. Crandall and Dr. McClung have disclosed no relevant financial relationships.

American Society for Bone and Mineral Research (ASBMR) 2012 Annual Meeting. Abstract 1024. Presented October 13, 2012.

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