Pitfalls in the external validation of FRAX.

SUMMARY

Recent studies have evaluated the performance of FRAX® in independent cohorts. The interpretation of most is problematic for reasons summarised in this perspective.

INTRODUCTION

FRAX is an extensively validated assessment tool for the prediction of fracture in men and women. The aim of this study was to review the methods used since the launch of FRAX to further evaluate this instrument.

METHODS

This covers a critical review of studies investigating the calibration of FRAX or assessing its performance characteristics in external cohorts.

RESULTS

Most studies used inappropriate methodologies to compare the performance characteristics of FRAX with other models. These included discordant parameters of risk (comparing incidence with probabilities), comparison with internally derived predictors and inappropriate use and interpretation of receiver operating characteristic curves. These deficits markedly impair interpretation of these studies.

CONCLUSION

Cohort studies that have evaluated the performance of FRAX need to be interpreted with caution and preferably re-evaluated.