The Frail'BESTest: an adaptation of the ``balance evaluation system test'' for frail older adults; Concurrent validity, responsiveness, validity for fall prediction and detection of slower walkers

Background The Frail'BESTest was developed in order to include frail older adults when they are using the BESTest. Recently, psychometrics properties (internal coherence, systems usefulness, complementarity and inter-rater reliability) of the Frail'BESTest were tested. To complete these analyses, this study will aim the assessment of its concurrent validity, responsiveness, predictive validity on falls occurrence, and slower walkers detection. Methods The correlation between the Frail'BESTest and the Gait Speed Test permitted to assess concurrent validity. The variation between the initial test score and the score obtained after the completion of a rehabilitation program was used to evaluate responsiveness with MANOVA analysis and standard response mean (SRM) calculation. Predictive validity was assessed with receiver-operating characteristic curves and area under the curve (AUC) analysis regarding falls occurrence. Slower walkers detection thresholds were computed by receiver-operating characteristic curves for the Frail'BESTest and the Tinetti test. Results The concurrent validity of the test was good (r = 0.74; p < 0.001). The Standard Error of measurement was at 2.81 points and the Minimal Detectable Change at 7.79 points for the total score of the Frail'BESTest. The SRM was at 0.41 for the Tinetti test and 0.56 for the Frail'BESTest. The AUC, computed according to fall occurrence, was at 0.71 for the Gait Speed test, 0.673 for the Tinetti test and 0.693 for the Frail'BESTest. Both the Tinetti (AUC = 0.87) and the Frail'BESTest (AUC = 0.88) were found suitable for tracking slower walkers. Conclusion Concurrent validity and responsiveness of the Frail'BESTest were good. As for the Tinetti and the Frail'BESTest, they were unable to predict efficiently falls occurrence in the tested sample. The Frail'BESTest seems enough sensitive to spot the slower walkers efficiently, using a 15/20 threshold method. The Frail'BESTest was found to be a valid and responsive clinical test, therefore it can be recommended as an outcome measure in clinical practice.