The FRAX tool in French women: How well does it describe the real incidence of fracture in the OFELY cohort?

Abstract

The FRAX tool estimates an individual's fracture probability over 10 years from clinical risk factors with or without bone mineral density (BMD) measurement. The aim of our study was to compare the predicted fracture probabilities and the observed incidence of fracture in French women during a 10-year follow-up. The probabilities of fracture at four major sites (hip, clinical spine, shoulder, or wrist) and at the hip were calculated with the FRAX tool in 867 women aged 40 years and over from the Os des Femmes de Lyon (OFELY) cohort.The incidence of fracture was observed over 10 years. Thus 82 women sustained 95 incident major osteoporotic (OP) fractures including 17 fractures at the hip. In women aged at least 65 years (n = 229), the 10-year predicted probabilities of fracture with BMD were 13% for major OP fractures and 5% for hip fractures, contrasting with 3.6% and 0.5% in women younger than 65 years (p < .0001). The predicted probabilities of both major OP and hip fractures were significantly higher in women with osteoporosis (n = 77, 18% and 10%) and osteopenia (n = 390, 6% and 2%) compared with women with normal BMD (n = 208, 3% and <1%; p < .0001. The predicted probabilities of fracture were two and five times higher in women who sustained an incident major OP fracture and a hip fracture compared with women who did not (p < .0001). Nevertheless, among women aged at least 65 years with low BMD values (T-score < or = -1; n = 199), the 10-year predicted probability of major OP fracture with BMD was 48% lower than the observed incidence of fractures (p < .01). A 10-year probability of major OP fracture higher than 12% identified more women with incident fractures than did BMD in the osteoporotic range (p < .05). In French women from the OFELY cohort, the observed incidence of fragility fractures over 10 years increased with age following a pattern similar to the predicted probabilities given by the FRAX tool. However, in women aged at least 65 years with low BMD, the observed incidence of fractures was substantially higher than the predicted probability.