The timed walk test as a measure of severity and survival in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a relentlessly progressive disease with a median survival of approximately 3 yrs. Measurements of airflow and lung volumes at rest are generally used to monitor the clinical course in this disorder. This study was designed to determine if a modified version of the 6-min walk test, called the timed walk test, accurately characterises disease severity and survival in IPF. The study population consisted of 28 patients with well-characterised progressive IPF. The timed walk test and concurrent measures of disease severity were assessed at baseline. Participants were prospectively followed for > or =4 yrs to determine the relationship between parameters of the timed walk test and survival. There were strong correlations between the end-exercise saturation and walk-velocity parameters of the timed walk test and diffusing capacity, and arterial oxygen tension at rest. In univariate Cox proportional-hazards models, end-exercise saturation, change in saturation with exercise, walk distance and walk velocity were associated with survival. In unadjusted logistic regression models, odds of death at 2 yrs were associated with the same parameters. In conclusion, the timed walk test relates to disease severity and long-term outcome in progressive idiopathic pulmonary fibrosis.