Development and Validation of a Risk Score to Predict the First Hip Fracture in the Oldest Old: A Retrospective Cohort Study

Abstract

BACKGROUND: To evaluate whether the common risk factors and risk scores (FRAX, QFracture and Garvan) can predict hip fracture in the oldest old (defined as age≥80), and to develop an oldest-old specific 10-year hip fracture prediction risk algorithm. METHODS: Subjects aged≥80 without history of hip fracture were studied. For the derivation cohort (N=251, mean age=83), participants were enrolled with a median follow-up time of 8.9 years. For the validation cohort (N=599, mean age=85), outpatients were enrolled with a median follow-up of 2.6 years. A 5-factor risk score (the HKOS score) for incident hip fracture was derived and validated, and its predictive accuracy was evaluated and compared with other risk scores. RESULTS: In the derivation cohort, the C-statistics were 0.65, 0.61, 0.65, 0.76 and 0.78 for FRAX with bone mineral density (BMD), FRAX without BMD, QFracture, Garvan, and the HKOS score, respectively. The category-less net reclassification index and integrated discrimination improvement of the HKOS score showed a better reclassification of hip fracture than FRAX and QFracture (all P<0.001) but not Garvan, while Garvan, but not HKOS score, showed a significant over-estimation in fracture risk (Hosmer-Lemeshow test p-value<0.001). In the validation cohort, the HKOS score had a C-statistic of 0.81 and a considerable agreement between expected and observed fracture risk in calibration. CONCLUSION: The HKOS score can predict 10-year incident hip fracture among the oldest old in Hong Kong. The score may be useful in identifying the oldest old patients at risk of hip fracture in both community-dwelling and hospital settings.