Abstract
INTRODUCTION: The six-minute-walk test (6MWT) is widely used in the functional evaluation of interstitial lung diseases (ILD). However, the clinical utility of some of the 6MWT measurements, such as the recovery period, have not been fully explored.
METHODS We retrospectively evaluated the association of 6MWT parameters with 1yr survival of 81 consecutive ILD patients (40 IPF/NSIP, 14 CTD, 27 other fibrotic ILD) by Cox-proportional hazard and logistic regression multivariate models. The following 6MWT parameters were considered: 6-minute walk distance (6MWD); pre & post 6MWT values and recovery time of SpO2, heart rate (HR), Borg dyspnoea score; desaturation ratio- [DR-] 1 (SpO2post/6MWD) and 2 (Recovery timeSpO2/6MWD). Disease severity was assessed by CPI [Wells et al, 2003].
RESULTS Except for older age in the IPF/NSIP group, there were no significant differences in gender, smoking status, and lung function parameters between disease groups. DR-1 (HR=6.05, 95% CI 2.04-18.02, p=0.001) was more tightly linked with survival, independently of disease severity and diagnosis, than other 6MWT predictors DR-2 (p=0.05) and 6MWD (p=0.05). Adding in turn single 6MWT parameters to a clinical model (CPI, diagnosis) of mortality conferred only marginal improvements, whereas significant changes were obtained adding both DR-1 and DR-2 (C-statistics 0.79 vs 0.69, p=0.03).
CONCLUSIONS Our results suggest that combined parameters of the 6MWT and analysis of the recovery period add prognostic information to 6MWD and baseline lung function. Prospective studies in large cohorts are warranted to confirm these findings.
- © 2014 ERS