Abstract
Ths object of this study was to examine validity, meaningful effect sizes, and patterns
of response of the Transition Dyspnea Index (TDI) in a clinical trial cohort of chronic
obstructive pulmonary disease (COPD) patients. The design was a retrospective analysis
of data from a randomized, double-blind placebo-controlled clinical trial. We analyzed
fifty clinical investigation sites in United States. There were 921 patients with
stable COPD. Tiotropium 18 μg dry powder or matching placebo was used. Patients were
allowed to remain on usual care less ipratropium bromide. Construct validity was demonstrated
by significant correlations (P < .05) between Baseline Dyspnea Index (BDI) and other
baseline measures, as well as between TDI and changes in other measures at the end
of 1 year. Concurrent validity was observed by the significant correlation between
TDI and dyspnea diary responses. Changes in TDI focal score were in the range of one
unit when the group was stratified by a minimal change in the physician's global evaluation.
Significantly less (P < .05) supplemental albuterol was observed in the group of responders
defined by a one-unit improvement in TDI. Responders also had few exacerbations and
better health status. The validity of the TDI is supported in a large clinical trial
setting. A one-unit change in the TDI focal score represented the minimal important
difference.
Keywords
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Article info
Publication history
Accepted:
June 6,
2002
Received in revised form:
April 25,
2002
Received:
December 14,
2001
Identification
Copyright
© 2003 Elsevier Science Inc. Published by Elsevier Inc. All rights reserved.
