The World Health Organization Fracture Risk Assessment Tool (FRAX) Underestimates Incident and Recurrent Fractures in Consecutive Patients With Fragility Fractures

Abstract

The World Health Organization Fracture Risk Assessment tool (FRAX) was developed to identify patients at risk of sustaining a fragility fracture (FF). The objective of the study was to evaluate estimated FRAX probabilities of FF at the time of a FF and to compare them with the observed incidence of recurrent FF. A prospective cohort included men and women older than 50 years at the time of a FF. FRAX scores without bone mineral density [FRAX-body mass index (BMI)] were calculated prior to and after the inclusion FF. Recurrent FFs were recorded over a 4-year follow-up. Determinants associated with recurrent FF were determined by univariate and multivariate analyses. FRAX-BMI scores were available in 1399 of the 1409 recruited patients. A high-risk FRAX-BMI score was present in only 42.7% patients before and 56.4% after the incident FF. Most FF patients at low or moderate risk before their initial FF were men, younger than 65 years, or without previous FF. Over a median follow-up of 3 years, recurrent FF occurred in 108 patients (2.69 per 100 patient-years). The overall sensitivity of post-FF FRAX to predict a recurrent FF was 71.3% and was specifically lower in patients younger than 65 years (13%) and without previous FF (63%) at inclusion. The FRAX-BMI scores were below the Canadian threshold for treatment in more than half the patients at the time of a FF and in close to a third of patients with recurrent FF. FRAX-BMI severely underestimates the FF risk in patients younger than 65 years old and after a single FF.