The Victorian Institute of Sport Assessment - Achilles is fundamentally flawed and unfit for clinical practice or research: A Rasch Measurement Theory Analysis using COSMIN recommendations.

OBJECTIVES

Evaluate structural validity, hypothesis testing and measurement invariance of the Victorian Institute of Sport Assessment-Achilles (VISA-A) using Rasch analysis to determine if it can be recommended to measure Achilles tendinopathy severity.

METHODS

We performed an evaluation of the VISA-A measurement properties using Rasch Measurement Theory by pooling individual participant data from previously conducted studies (n = 217). Structural validity was assessed via threshold/category mean order; adequate item fit; unidimensionality; local dependence; internal consistency. Hypothesis testing was assessed via divergent validity. Measurement invariance assessed via differential item functioning.

RESULTS

The VISA-A has inadequate construct validity. This is evident from issues with item 8 and insufficient threshold order, item fit, borderline internal consistency and measurement invariance, with item response being influenced by both age and BMI.

CONCLUSION

The VISA-A has inadequate structural validity, borderline internal consistency and poor measurement invariance. Thus, the VISA-A does not meet with COSMIN criteria for construct validity due to issues with structural validity and measurement invariance. Thus, the VISA-A cannot be recommended for use, and should not be used in clinical practice or research. However, if the VISA-A has been used, analysis using only items 1-6, with responses collapsed into a 4-point scale provides the best structural validity.