Original articleUpdating the Minimal Important Difference for Six-Minute Walk Distance in Patients With Chronic Obstructive Pulmonary Disease
Section snippets
Methods
Patients who were referred for pulmonary rehabilitation at 2 tertiary hospitals were invited to participate. Patients were eligible if they had a diagnosis of COPD confirmed on spirometry15 and were in a stable clinical state. Patients were excluded if they had comorbidities that prevented exercise training (severe cardiac or neurologic conditions, severe osteoarthritis). The study was approved by the human research ethics committees of both institutions.
Results
Seventy-nine participants were recruited; 4 participants did not complete the program and did not return for final assessment. Demographic characteristics of the 75 included participants (44 men) are in table 1. Ten participants had mild disease, 30 had moderate disease, 23 had severe disease, and 12 had very severe disease.23 There was a wide range of 6MWDs (104–523m).
Discussion
This study has shown that in patients with COPD and a wide range of disease severity, the MID for the 6MWD is approximately 25 meters. This result was consistent across anchor-based and distribution-based methods. A change in 6MWD of 14% of baseline walking distance may also be important to patients; however, this criterion is less sensitive. Patient and clinician estimates of clinically important change were similar.
This is the first study that we know of to prospectively evaluate the MID for
Conclusions
The MID for 6MWD in COPD is approximately 25 meters. A change in 6MWD of 14% also represents an important effect; however, this threshold is less sensitive than the absolute change in distance. The identification of an MID for 6MWD supports the continued use of the six-minute walk test to identify patient-important change in research and clinical practice.
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