Trinity amputation and prosthesis experience scales: a psychometric assessment using classical test theory and rasch analysis.

OBJECTIVE

To perform a detailed psychometric analysis using both classical test theory and Rasch analysis of the three main scales of the Trinity Amputation and Prosthesis Experience Scales (TAPES) in people with a lower-limb amputation.

DESIGN

A sample of 498 persons who were prosthesis users with a lower-limb amputation was retrospectively studied, pooled from a number of studies undertaken across the United Kingdom and Ireland in the past decade in which the TAPES had been completed as part of a postal survey. Both factor analysis techniques and Rasch analysis were performed on TAPES data. Dimensionality, item fit to the model, response category performance, and internal construct validity were assessed. Category collapsing and item removal were considered to improve the questionnaire.

RESULTS

The analyses suggested to restructure the TAPES as follows: (a) three psychosocial adjustment subscales with a four-point rating scale (and a reworded item); (b) an activity restriction scale based on ten items with their original three-point rating scale; and (c) two satisfaction with the prosthesis subscales using a three-point rating scale. All scales and subscales showed acceptable internal consistency and ability to define a distinct hierarchy of persons along the measured construct.

CONCLUSIONS

This study empirically identified a revised version of the TAPES (TAPES-R) with a simplified general structure and psychometrically suitable for assessing the complex experience of amputation and adjustment to a lower-limb prosthesis. Additional studies are needed to confirm and further explore its measurement properties in other samples, thereby adding clinical validity to the instrument.