E-Poster Presentation ESA-SRB-ANZBMS 2021

External validation of a risk assessment tool for predicting fragility fractures and mortality in the Osteoporotic Fractures in Men (MrOS) Study (#766)

Thach Tran 1 , Dana Bliuc 1 , Robert Blank 1 , Weiwen Chen 1 , John Eisman 1 , Kristine Ensrud 2 , Lisa Langsetmo 2 , Tuan Nguyen 1 , Jacqueline Center 1
  1. Garvan Institute of Medical Research, Darlinghurst, NSW, Australia
  2. Division of Epidemiology and Community Health, University of Minnesota, Minneapolis, MN, USA

Background: Existing fracture prediction tools are not designed to predict fracture-related consequences. We have developed a risk assessment tool1 to predict fractures and mortality using the Dubbo Osteoporosis Epidemiology Study and the Canadian Multicentre Osteoporosis Study. The tool requires external validation for widespread use.

Objective:       to quantify the accuracy of the tool in predicting initial fractures, subsequent fractures and mortality in the MrOS USA cohort.

Methods:        5,994 MrOS men aged 74 (±5.9) years were followed for fractures and mortality. Baseline predictors included age, bone mineral density, prior falls, prior fracture, cardiovascular and respiratory diseases, diabetes, hypertension and cancer. Predicted 5- and 10-year transition risks to initial fractures, subsequent fractures and mortality were estimated. Discrimination ability was assessed using the Harrell’s C index, and calibration assessed by dividing the cohort into centiles of predicted risk and comparing the observed and predicted risk.

Results:           During a median follow-up time of 14 years (IQR:8-17), there were 1,085 initial incident fractures (~15.5 fractures/1,000 person-years; 95%CI: 15.6-16.5) followed by 236 subsequent fractures (46.7; 40.9-53.1). Mortality rates among subjects with no fracture, an initial and subsequent fracture were 4.8 deaths/100 person-years (95%CI: 4.6-4.9), 11.8 (10.4-12.7), and 19.4 (16.5-22.6), respectively. Baseline predictors remained significant in the MrOS cohort. The tool had moderate discrimination ability with the highest concordance documented for predicting deaths (C index: 0.75), any initial fracture (0.70) or hip fracture (0.74). Importantly, the tool accurately predicted transition risks to initial fractures, subsequent fractures and post-fracture deaths. However, it overestimated the risk to death from those not suffering fracture, possibly due to substantial between-cohort differences in baseline mortality risk (Fig). 

Conclusions: The risk assessment tool provided moderate discrimination and accurate calibration for predicting fractures and fracture-related mortality in men. Subsequent validation in women is necessary prior to consideration of its use in clinical practice settings.

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