Psychometric Properties of a New Measure of Upper Limb Performance in Post-Stroke Individuals: Trunk-Based Index of Performance.

Abstract

Background: Several measures of upper limb (UL) motor tasks have been developed to characterize recovery. However, UL performance and movement quality measures in isolation may not provide a true profile of functional recovery.

Objective: To investigate the measurement properties of a new trunk-based Index of Performance (IPt) of the UL combining endpoint performance (accuracy and speed) and movement quality (trunk displacement) in stroke.

Methods: Participants with stroke (n = 25, mean time since stroke: 18.7 ± 17.2 months) performed a reaching task over 3 evaluation sessions. The IPt was computed based on Fitts' Law that incorporated endpoint accuracy and speed corrected by the amount of trunk displacement. Test-retest reliability was analyzed using intraclass correlation coefficient (ICC) and Bland-Altman plots. Standard error of measurement (SEM) and Minimal Detectable Change (MDC) were determined. Validity was investigated through the relationship between IPt, Fugl-Meyer Assessment (FMA-UE), and Action Research Arm Test (ARAT), as well as the ability of IPt to distinguish between levels of UL motor impairment severity.

Results: Test-retest reliability was excellent (ICC = .908, 95% CI: 0.807-0.96). Bland-Altman did not show systematic differences. SEM and MDC₉₅ were 14% and 39%, respectively. Construct validity was satisfactory. The IPt showed low-to-moderate relationships with FMA-UE (R² ranged from .236 to .428) and ARAT (R² ranged from .277 to .306). IPt scores distinguished between different levels of UL severity.

Conclusions: The IPt showed evidence of good reliability, and initial validity. The IPt may be a promising tool for research and clinical settings. Further research is warranted to investigate its validity with additional comparator instruments.