RT Journal Article
SR Electronic
T1 The 6 minute walk in idiopathic pulmonary fibrosis: longitudinal changes and minimum important difference
JF Thorax
JO Thorax
FD BMJ Publishing Group Ltd and British Thoracic Society
SP 173
OP 177
DO 10.1136/thx.2009.113498
VO 65
IS 2
A1 Jeffrey J Swigris
A1 Frederick S Wamboldt
A1 Juergen Behr
A1 Roland M du Bois
A1 Talmadge E King
A1 Ganesh Raghu
A1 Kevin K Brown
YR 2010
UL http://thorax.bmj.com/content/65/2/173.abstract
AB Rationale The response characteristics of the 6 minute walk test (6MWT) in studies of idiopathic pulmonary fibrosis (IPF) are only poorly understood, and the change in walk distance that constitutes the minimum important difference (MID) over time is unknown.Objectives To examine changes over time in distance walked (ie, 6MWD) during the 6MWT and to estimate the change in distance that constitutes the MID in patients with IPF.Methods Data from a recently completed trial that included subjects with IPF who completed the 6MWT, Saint George's Respiratory Questionnaire (SGRQ) and forced vital capacity (FVC) at 6 and 12  months were used to examine longitudinal changes in 6MWD. Both anchor- and distribution-based approaches as well as linear regression analyses were used to determine the MID for 6MWD. The SGRQ Total score and FVC were used as clinical anchors.Main results Among 123 subjects alive and able to complete the 6MWT at both follow-up time points, 6MWD did not change significantly over time (378.1 m at baseline vs 376.8 m at 6 months vs 361.3 m at 12 months, p=0.5). The point estimate for the 6MWD MID was 28 m with a range of 10.8–58.5 m.Conclusion In a group of patients with IPF with moderate physiological impairment, for those alive and able to complete a 6MWT, 6MWD does not change over 12 months. At the population level, the MID for 6MWD appears to be ∼28 m. Further investigation using other anchors and derivation methods is required to refine estimates of the MID for 6MWD in this patient population.