McCloskey EV et al. (2008) Ten-year fracture probability identifies women who will benefit from clodronate therapy—additional results from a double-blind, placebo-controlled randomised study. Osteoporos Int [doi:10.1007/s00198-008-0786-9]

Although low BMD is often an indicator for treatment to reduce fracture risk, concern exists that BMD alone is not sufficiently sensitive to indicate fracture risk. The WHO have developed an algorithm, FRAX® (University of Sheffield, UK) that uses clinical risk factors with or without BMD to estimate 10-year fracture probability. A 3-year study by McCloskey et al. has found that FRAX® identifies women at high risk of fracture, and also found that efficacy of clodronate treatment was greatest in those with highest risk of fracture.

The study population comprised 3,974 women aged 75 years or more who were recruited randomly from general-practice lists. The 10-year probability of a major osteoporotic fracture was derived from the following risk factors: age; BMI; history of prior fragility fracture; maternal history of hip fracture; rheumatoid arthritis; oral glucocorticoid use; and smoking. Participants were randomly assigned 800 mg clodronate daily, or placebo. The observed incidence of osteoporotic fractures increased with 10-year risk (calculated with the FRAX® algorithm). The greatest impact of clodronate in fracture-risk reduction was in those at greatest risk. For example, at a calculated, 10-year fracture probability of 15%, clodronate treatment was associated with a relative risk of 0.92; at 24% probability, treatment produced a relative risk of 0.73. Treatment efficacy correlated inversely with BMI; no other risk factor affected treatment efficacy.

The authors conclude that FRAX® can identify women at high risk of fracture and who will benefit from bisphosphonate treatment.