Minimal Clinically Important Differences in the Six-Minute Walk Test and the Incremental Shuttle Walking Test

Abstract

Simple walking tests are widely used for the assessment of functional status in patients with cardiorespiratory disorders. These tests require far less instrumentation than formal cardiopulmonary exercise tests, but they do require standardization of procedures to achieve reproducible results. The most widely used tests for patients with COPD are the 6-minute walking test (6MWT) and the incremental shuttle walking test (SWT). The 6MWT has been characterized in COPD patients with respect to reproducibility and responsivity to change in health status. The 6MWT results are correlated with pulmonary function, health-related quality of life, maximum exercise capacity, and mortality. The minimal clinically important difference (MCID) for the 6MWT is conservatively estimated to be 54-80 meters using both distributional and discriminative methods. For an individual patient, the 6MWT would need to change by about 86 meters to be statistically confident that there has been a change. The SWT has been less extensively validated than the 6MWT, but has similar reproducibility in COPD (CV = approximately 20%). The SWT results improve with pulmonary rehabilitation and bronchodilation, and are highly correlated with maximum oxygen consumption. There are no studies that address the issue of MCID for the SWT. In addition to the MCID, the design and interpretation of COPD clinical trials should take into account the severity of initial impairment, the asymmetry between positive and negative changes, the proportion of patients who show substantial improvement, and the costs and risks of the treatment.

Application of self-report and performance-based outcome measures to determine functional differences between four categories of prosthetic feet

“…Agrawal et al found that the Proprio foot promoted higher symmetry in level walking between the intact and prosthetic limb than other prosthetic feet [43]. Other benefits of the Proprio foot on functional activities such as ascending and descending stairs and ramps have been described in the literature [27][28].…”

“…The 6MWT has become one of the most widely used performance-based outcome measures of functional mobility and exercise capacity in a wide variety of populations because of its construct, low cost, and convenience to administer [27]. The 6MWT has been found to be effective in determining functional capacity using peak oxygen uptake [27][28]; predicting community ambulation capacity [29]; and assessing overall performance, mobility, and cardiovascular fitness [30].…”

“…The 6MWT has been found to be effective in determining functional capacity using peak oxygen uptake [27][28]; predicting community ambulation capacity [29]; and assessing overall performance, mobility, and cardiovascular fitness [30]. More recently, contributing variables such as hip extensor strength, age, single-limb balance time, and symmetry of step length have been found to correlate with 6MWT performance in people with amputation [31].…”

The Chitranjan Ranawat Award: The Nonoperated Knee Predicts Function 3 Years after Unilateral Total Knee Arthroplasty

“…The 6-minute walk test was originally described as a measure of respiratory fitness [3]. Controls walked at least 100 m further than patients after TKA at both intervals, a difference considered clinically meaningful [35]. Patients with osteoarthritis may have decreased cardiovascular status compared to controls [25], and while cardiovascular fitness may improve after TKA [26], it was not tested in this investigation.…”

September 2007 Letters to the Editor-in-Chief

“…Authors of commentaries 2,5,10 regarding methods for derivations of MCIDs make no exceptions for scales that produce normally distributed scores. In fact, cut scores using MCIDs are recommended for a number of outcome scales that typically produce normal distributions: gait velocity, 8 timed walking tests, 11 pain VAS, 6 Oswestry, 4 WOMAC, 1 etc. Also, in the diagnostic and prognostic literature it is common to use receiver-operator characteristic curve analysis to produce cut scores for normally distributed scales in order to define a positive versus negative diagnostic test, or a threshold for a prognostic factor.…”