Structural validity of the Trunk Assessment Scale for Spinal Cord Injury (TASS) with Rasch analysis for individuals with spinal cord disorders

The Journal of Spinal Cord Medicine, 2025 · DOI: 10.1080/10790268.2023.2256515 · Published: September 19, 2023

Spinal Cord Injury Rehabilitation Research Methodology & Design

Simple Explanation

The Trunk Assessment Scale for Spinal Cord Injury (TASS) was developed to evaluate trunk function in individuals with tetraplegia without interference from their upper-limb function. The TASS differs significantly from the TCT-SCI in two ways; the TASS prohibits the use of the upper limbs for postural maintenance, and it includes tasks that assess the trunk displacement distance regardless of upper limb dysfunction. A Rasch analysis was used to determine the structural validity of the TASS, evaluating its unidimensionality, fit statistics, category probability curve, ceiling/floor effects, local independence, reliability, and difference item function (DIF).

Study Duration

December 2019 and April 2022

Participants

104 Japanese individuals with a spinal cord injury

Evidence Level

Not specified

Key Findings

1
The TASS was observed to be a unidimensional and highly reproducible scale of item difficulty hierarchy that sufficiently identifies the superiority of the examinee’s ability.
2
The TASS showed a floor effect, and most of the non-scorers were individuals with a complete SCI.
3
One TASS item was a misfit based on the infit and outfit mean square; another item also showed a DIF contrast for age.

Research Summary

This study statistically confirms the structural validity of the Trunk Assessment Scale for Spinal Cord Injury (TASS) using Rasch analysis. The TASS is a unidimensional scale with good person and item separation, making it suitable for individuals with incomplete SCI; however, it faces challenges like a floor effect and item misfitting. The study suggests improvements to the TASS to enhance its utility, including modifying items and addressing the floor effect to better serve individuals with complete SCI.

Practical Implications

Clinical Goal Setting

The keyform illustrates the relationships between the categories of each item, aiding in setting short-term and long-term therapy goals based on the patient's ability level.

Scale Modification

The study identifies specific items in the TASS that may need synthesis or modification to improve its accuracy and relevance for individuals with spinal cord injuries.

Targeted Application

The TASS may be more suitable for individuals with incomplete spinal cord injuries due to the observed floor effect among those with complete injuries, guiding clinicians in selecting appropriate assessment tools.

Study Limitations

1
The sample was recruited from two centers in Japan, limiting generalizability to other countries.
2
The sample size was considered insufficient to ensure the robustness of the difference item function (DIF).
3
The contents of the TASS were not modified in this study, indicating a need for future modifications.

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