# Estimating the Responsiveness and Minimal Important Change of the Trunk Impairment Scale in Inpatients With Subacute Stroke Requiring Dependent Ambulation

## TL;DR

This study evaluates how well the Trunk Impairment Scale measures changes in balance for stroke patients needing help walking.

## Contribution

The first evaluation of the Trunk Impairment Scale's responsiveness and minimal important change in subacute stroke patients requiring ambulation assistance.

## Key findings

- The Trunk Impairment Scale showed significant differences between groups with and without meaningful improvement.
- The Trunk Impairment Scale had a minimal important change of 2.5 points and outperformed the Trunk Control Test in responsiveness.
- The Trunk Control Test showed ceiling effects and low correlation with balance improvements.

## Abstract

Introduction

The Trunk Impairment Scale (TIS) has gained attention as a comprehensive tool for evaluating static and dynamic sitting balance, as well as trunk coordination. In particular, the responsiveness and minimal important change (MIC) of the TIS, specifically in patients with subacute stroke requiring dependent ambulation, have not yet been clearly established. The primary objective of this study was to determine the responsiveness and MIC of the TIS in patients with subacute stroke requiring dependent ambulation. A secondary objective was to compare the measurement properties of the TIS with those of the Trunk Control Test (TCT), a simpler and widely used tool, in order to identify which is more appropriate for detecting changes in trunk function in this specific patient population.

Methods

A retrospective cohort study was conducted involving 32 patients with subacute stroke. Eligible participants were diagnosed with cerebral infarction, cerebral hemorrhage, or subarachnoid hemorrhage and had a Functional Ambulation Category (FAC) score of 3 or lower, indicating a need for assistance with ambulation. All participants were assessed at admission and approximately one month later using the TIS, TCT, and Berg Balance Scale (BBS). MIC was calculated using receiver operating characteristic (ROC) curve analysis. Patients who improved by 5 or more points on the BBS were classified as the "important change group", while those with less than a 5-point improvement were classified as the "non-important change group". Responsiveness was analyzed through Spearman's correlation for score changes, skewness analysis for ceiling and floor effects, and unpaired t-tests between groups. MIC was calculated only when both the correlation coefficient (ρ) was ≥0.3 and the area under the ROC curve (AUC) was ≥0.7.

Results

The change in TIS scores differed significantly between the important and non-important change groups (p=0.001), and a moderate correlation was observed with BBS score changes (ρ=0.495; p<0.001). Skewness analysis showed no ceiling effect for the TIS. The AUC of the ROC curve for the TIS was 0.776 (95% CI: 0.612-0.941), and the MIC was calculated to be 2.5 points (95% CI: 0.5-4.0). In contrast, the TCT showed no significant difference in change scores (p=0.968). Ceiling effects were observed at both admission (37.5%) and follow-up (43.8%), the correlation with BBS was low (ρ=0.197; p=0.280), and the AUC was also low at 0.518, failing to meet the criteria for MIC calculation.

Conclusion

This is the first study to evaluate the responsiveness and MIC of the TIS in a clearly defined population of patients with subacute stroke who require assistance with ambulation. The MIC of 2.5 points observed in this study may serve as a potentially useful reference for clinical interpretation. Moreover, the findings suggest that the TIS is a more useful assessment tool than the TCT for evaluating trunk function in patients with subacute stroke requiring ambulation assistance.