External validation of FRISBEE 2-year and 5-year fracture prediction models in a fracture liaison service cohort.

UNLABELLED: We externally validated the FRISBEE models of 2-year and 5-year fracture risk prediction in 517 women with index fractures. Both models overestimated the fracture risk. Recalibration of the FRISBEE models are needed before use in Norwegian women with recent fractures.

PURPOSE: We externally validated the Fracture Risk Brussels Epidemiological Enquiry (FRISBEE) groups' 2-year and 5-year fracture risk models.

METHODS

We included women above 50 years with a recent fracture from the consent-based part of the Norwegian Capture the Fracture Initiative study (NoFRACT). They had bone mineral density assessed and filled in a questionnaire including risk factors for fracture at baseline between October 2015 and December 2017. We calculated and validated the 2-year and 5-year fracture risk using the FRISBEE equation models.

RESULTS

Of 517 women aged 65.5 ± 8.6 years with fractures, 94 (18%), 55 (11%), and 31 (6%) sustained a subsequent fracture of any type, major osteoporotic fractures (MOF), or central fracture, during 4.7 ± 1.3 years mean follow-up. The area under the receiver-operating curve (AUC) (95% confidence interval (CI)) for any type of fracture, MOF, and central fracture was 0.57 (0.51-0.63), 0.57 (0.46-0.67), and 0.65 (0.53-0.77), respectively, for the FRISBEE 2-year risk models and 0.57 (0.51-0.64), 0.58 (0.50-0.67), and 0.67 (0.57-0.76) for the FRISBEE 5-year risk models. The calibration slopes (with 95% CI) that compared observed vs. predicted probabilities for fracture across deciles of risk for any type of fracture, MOF, and central fracture were all low: 0.34 (0.02-0.64), 0.33 (- 0.09-0.74), and 0.61 (0.16-1.06), in the FRISBEE 2-year models, and 0.54 (0.13-0.95), 0.43 (0.05-0.80), and 0.69 (0.31-1.08), in the FRISBEE 5-year models.

CONCLUSION

Overall, the FRISBEE models overestimated both 2-year and 5-year fracture risk. Recalibration is needed before these models can be used in Norwegian women with recent fractures.