Meaningful gait speed improvement during the first 60 days poststroke: minimal clinically important difference

Abstract

Background: When people with stroke recover gait speed, they report improved function and reduced disability. However, the minimal amount of change in gait speed that is clinically meaningful and associated with an important difference in function for people poststroke has not been determined.

Objective: The purpose of this study was to determine the minimal clinically important difference (MCID) for comfortable gait speed (CGS) associated with an improvement in the modified Rankin Scale (mRS) score for people between 20 to 60 days poststroke.

Design: This was a prospective, longitudinal, cohort study.

Methods: The participants in this study were 283 people with first-time stroke prospectively enrolled in the ongoing Locomotor Experience Applied Post Stroke (LEAPS) multi-site randomized clinical trial. Comfortable gait speed was measured and mRS scores were obtained at 20 and 60 days poststroke. Improvement of >or=1 on the mRS was used to detect meaningful change in disability level.

Results: Mean (SD) CGS was 0.18 (0.16) m/s at 20 days and 0.39 (0.22) m/s at 60 days poststroke. Among all participants, 47.3% experienced an improvement in disability level >or=1. The MCID was estimated as an improvement in CGS of 0.16 m/s anchored to the mRS.

Limitations: Because the mRS is not a gait-specific measure of disability, the estimated MCID for CGS was only 73.9% sensitive and 57.0% specific for detecting improvement in mRS scores.

Conclusions: We estimate that the MCID for gait speed among patients with subacute stroke and severe gait speed impairments is 0.16 m/s. Patients with subacute stroke who increase gait speed >or=0.16 m/s are more likely to experience a meaningful improvement in disability level than those who do not. Clinicians can use this reference value to develop goals and interpret progress in patients with subacute stroke.

Figures

Figure 1.

(a) A 2 × 2 table traditionally used to calculate sensitivity and specificity. The sample population is divided into 4 groups (cells A, B, C, and D). Cell A represents the number of participants who had a positive result on both the gold standard test and the new test (true positives). Cell B represents the number of participants who had a positive result on the gold standard test but a negative result on the new test (false negatives). Cell C represents the number of participants who had a negative result on the gold standard test but a positive result on the new test (false positives). Cell D represents the number of participants who had a negative result on both the gold standard test and the new test (true negatives). (b) A 2 × 2 table of actual data from this study for the gold standard anchor (the modified Rankin Scale) and the minimal clinically important difference (MCID) of 0.16 m/s for comfortable gait speed. (c) Formulas used to calculate sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio and actual data used to calculate values for the MCID of 0.16 m/s for comfortable gait speed.

Figure 2.

Receiver operating characteristic (ROC) curve for the ability of change in gait speed to detect a change in modified Rankin Scale (mRS) scores. The ROC curve provides a visual depiction of the sensitivity (y-axis) and specificity (x-axis) of gait speed cutoff scores for detecting ≥1 level of improvement in mRS scores. Each point along the curve represents a change in gait speed for which sensitivity and specificity were calculated.

Figure 3.

Nomogram graphical representation of the probability that an individual with stroke will experience a meaningful change in disability level. The green line plots the pretest probability estimated at 47% (based on the overall percentage of participants in this study with improved disability level) and the positive likelihood ratio (LR+) used when an individual meets or exceeds the minimal clinically important difference (MCID) of 0.16 m/s for comfortable gait speed to determine the posttest probability that the individual has a 60% probability of experiencing an improvement in disability level. The red line plots the pretest probability and the negative likelihood ratio (LR–) used when an individual does not meet the MCID of 0.16 m/s for comfortable gait speed to determine the posttest probability that the individual has only a 29% probability of experiencing an improvement in disability level. Likelihood ratio nomogram adapted and reprinted with permission from the Centre for Evidence-Based Medicine, Oxford, United Kingdom.