Test-Retest Reliability and Minimal Detectable Change of Body Function Impairment and Activity Limitation Outcomes Using a Mechatronic Evaluation Designed for Inpatient Stroke Research

Abstract

Objective

To determine the test-retest reliability and minimal detectable change (MDC) scores for 7 precision measures examining upper extremity strength, reaching ability, and the expression of flexion synergy after stroke. The measurements relied on a mechatronic evaluation designed for time efficiency facilitating implementation in inpatient translational research.

Design

Observational, analytical, cross-sectional study.

Setting

University research laboratory.

Participants

Twenty-five participants (N=25) >6 months poststroke with persistent upper extremity body function impairment and activity limitation were recruited using convenience sampling.

Interventions

Not applicable.

Main Outcome Measures

Shoulder abduction and elbow extension strength measured as a unit of torque (Nm); normalized reaching distance with the arm under 3 conditions: supported, against gravity, and against 50% of shoulder abduction strength; flexion synergy takeover; and emergence thresholds.

Results

Twelve male and 13 female participants aged 56.4 ± 17.8 years with a mean time poststroke of 5.37 ± 7.55 years completed the study. The intraclass correlation coefficients for the outcome measures were as follows: shoulder abduction strength (0.963), elbow extension strength (0.983), supported reaching (0.982), reaching against gravity (0.968), reaching against 50% abduction strength (0.974), flexion synergy takeover (0.919), and flexion synergy emergence (0.949) thresholds. The MDC, overall mean, and standard deviation were calculated as follows: shoulder abduction strength (5.69 Nm, 24.44±10.67 Nm), elbow extension strength (5.66 Nm, 18.53±15.66 Nm), supported reaching (0.07, 0.91±0.20), reaching against gravity (0.15, 0.73±0.30), reaching against 50% abduction strength (0.13, 0.69±0.29), flexion synergy takeover (0.14, 0.91±0.17), and flexion synergy emergence (0.17, 0.56±0.27) thresholds.

Conclusions

The mechatronic evaluation, although streamlined from more labor-intensive laboratory evaluations, demonstrates excellent (>0.90) test-retest reliability and MDC scores for 7 precision measures of upper extremity body function impairment (weakness and synergy) and activity limitation (reaching).