Performance of FRAX in a cohort of community-dwelling, ambulatory older men: the Osteoporotic Fractures in Men (MrOS) study

We evaluated performance of FRAX in older men who participated in the Osteoporotic Fractures in Men (MrOS) study. FRAX has been extensively studied in women, but there are few studies of its performance in men. FRAX estimates for 10-year hip fracture and major osteoporotic fracture (MOF; either hip, clinical spine, forearm, or shoulder) were calculated from data obtained from MrOS participants and compared to observed 10-year fracture cumulative incidence calculated using product limit estimate methods, accounting for competing mortality risk. Five thousand eight hundred ninety-one men were followed for an average of 8.4 years. Without bone mineral density (BMD) in the FRAX model, the mean 10-year predicted fracture probabilities for hip and MOF were 3.5 % and 8.9 %, respectively; addition of BMD to the calculations reduced these estimates to 2.3 % and 7.6 %. Using FRAX without BMD, predicted quintile probabilities closely estimated cumulative incidence of hip fracture (range of observed to predicted ratios 0.9-1.1). However, with BMD in the FRAX calculation, observed to predicted hip fracture probabilities were not close to unity and varied markedly across quintiles of predicted probability. For MOF, FRAX without BMD overestimated observed cumulative incidence (range of observed to predicted ratios 0.7-0.9) and addition of BMD did not improve this discrepancy (range of observed to predicted ratios 0.7-1.1). Addition of BMD to the calculation had mixed effects on the discriminatory performance of FRAX, depending on the analysis tool applied. Among this cohort of community-dwelling older men, the FRAX risk calculator without BMD was well calibrated to hip fracture but less well to MOF.