Evaluating the performance of the Charlson Comorbidity Index (CCI) in fracture risk prediction and developing a new Charlson Fracture Index (CFI): a register-based cohort study

The Charlson Comorbidity Index (CCI) may be applicable for predicting fracture risk since several diagnoses from the index are predictors of fracture. Main results were that the CCI was updated to predict risk of hip fracture with fair precision and that the index could be useful in detecting high-risk individuals.

PURPOSE: Several of the Charlson Comorbidity Index (CCI) diagnoses are validated predictors of fracture. The purpose of this study was to evaluate the performance of the CCI 1987 by Charlson et al. and of the CCI 2011 by Quan et al. in predicting major osteoporotic fracture (MOF) and hip fracture (HF). Furthermore, it was examined whether the index could be modified to improve fracture risk prediction.

METHODS: The study population included the entire Danish population aged 45 + years as per January 1, 2018. The cohort was split randomly 50/50 into a development and a validation cohort. CCI diagnoses and fracture outcomes were identified from hospital diagnoses. The weighting of diagnoses was updated in a new Charlson Fracture Index (CFI) using multivariable logistic regression. Predictive capabilities of the CCI 1987, the updated CCI 2011 and the new Charlson Fracture index were evaluated in the validation cohort by receiver operating characteristics (ROC) curves and area under the curve (AUC).

RESULTS: In the validation cohort, the 1987 and 2011 CCIs resulted in AUCs below or around 0.7 in prediction of MOF and HF in both sexes. The CFI resulted in AUCs < 0.7 in prediction of MOF in both sexes. In prediction of HF, the CFI resulted in AUC of 0.755 (95% CI 0.749; 0.761) in women and 0.782 (95% CI 0.772; 0.793) in men.

CONCLUSION: The 1987 and 2011 CCIs showed overall poor accuracy in fracture risk prediction. The CFI showed fair accuracy in prediction of HF in women and in men.