Comparison of the areas under the receiver operating characteristic (ROC) curves of the four frailty instruments compared.*

AUC: areas under curve; SE: standard error; CI: confidence interval; MPI: Multidimensional Prognostic Index; FI-SOF: Frailty Index derived from the Study of Osteoporotic Fractures; FI-CD: Frailty Index based on cumulative deficits; FI-CGA: Frailty Index based on a Comprehensive Geriatric Assessment.*AUCs were assessed by crude and adjusted logistic regression models, accounting for clustering due to centre effect.