Abstract
Introduction: The 6MW is used to assess interventions in COPD but existing estimates of the MCID for have been derived from narrow cohorts where a non-blinded intervention, for example pulmonary rehabilitation, have been applied.
Objective: To define the MCID for 6MW distance in an unselected population.
Methods: Data from the ECLIPSE cohort were used. Briefly 2112 patients were prospectively followed for 3 years in a multicentre study. We defined an index event as death or first hospitalisation and calculated the change in 6MW (Δ6MW) in the last 12 month period before the event occurred. If a patient did not have an event the last 12 month change was used. We also related Δ6MW to commonly used outcome measures in COPD; FEV1 and St Georges Respiratory Questionnaire (SGRQ-C).
Results: Of the subjects with Δ6MW, 94 patients died and 323 were hospitalised. 6MW fell by mean (SD) 29.7 (82.9)m more in those who died than survivors (p<0.001). No significant difference in Δ6MW was observed in those who had a first hospitalisation than those who did not. Cox proportional hazard modelling showed that a Δ6MW of more than –30m conferred a hazard ratio of 1.93 (95% CI: 1.29, 2.90; p=0.001) for death. Weak relationships only were observed between Δ6MW and ΔFEV1 or Δ SGRQ.
Conclusions: A fall in 6MW of 30m or more is associated with increased risk of death in patients with COPD and therefore represents a clinically significant MCID for this test. The modest relationships between Δ6MW and ΔFEV1 or Δ SGRQ suggest that anchor based methods for determining MCID are context dependent.
Funded by GSK (SCO104960; NCT00292552).
- © 2012 ERS
