Minimal important difference of the transition dyspnoea index in a multinational clinical trial

Abstract

Dyspnoea is a primary symptom of chronic obstructive pulmonary disease (COPD). The baseline (BDI) and transition (TDI) dyspnoea indices are commonly used instruments to assess breathlessness and the impact of intervention. Its validity and pattern of response in multinational clinical trials has not been established.In a retrospective analysis of a cohort of 997 COPD patients who received tiotropium, salmeterol or placebo, in addition to usual care, the validity and pattern of response of the BDI and TDI were examined.The BDI was significantly correlated with the dyspnoea diary (DD) score and the symptom and activity components of the St. George9s respiratory questionnaire (SGRQ), establishing concurrent validity. Furthermore, the TDI was also correlated with the changes in DD, SGRQ symptom and activity scores. Construct validity was established by the association between baseline forced expiratory volume in one second (FEV1) and BDI and DFEV1 with TDI. Physician9s global evaluation (PGE) was significantly associated with BDI as well as DPGE with TDI. Significant correlations have also been observed when the cohorts were classified according to native English and native non-English speaking countries. A change in PGE of 1 category (i.e. 2 units on an 8-point scale) was associated with a mean TDI of y1 unit (0.9-1.3 mean focal score), lending further support to the clinical significance of this change inherent in the instrument9s descriptors. TDI responders (i.e. focal score ¢1 unit) used less supplemental salbutamol, had fewer exacerbations and had significantly improved health status as measured by impacts and total SGRQ scores compared with nonresponders.In conclusion, the transition dyspnoea index is a valid instrument when used in a multinational clinical trial and the patterns of response confirm a 1-unit change in the transition dyspnoea index focal score as being clinically important.

Effects of tiotropium on lung hyperinflation, dyspnoea and exercise tolerance in COPD

“…Moreover, patients in the present study were capable of exercising for a longer duration at higher V9E without any further increase in dyspnoea. Finally, there were parallel improvements in TDI, by an average of 1.7 units, as compared to placebo, indicating clinically relevant reductions in chronic activity-related dyspnoea and functional capacity [32,33]. A further indication of a beneficial effect of tiotropium on dyspnoea was the reduced requirement for reliever shortacting bronchodilators throughout the course of the study in this group.…”

Blinded 12-week comparison of once-daily indacaterol and tiotropium in COPD

“…It is therefore necessary to make a judgement on the clinical relevance of differences between the treatments for the clinical outcomes assessed. This judgement must necessarily be subjective, since reported minimal clinically important differences (MCID) and clinically relevant changes were derived on the basis of differences versus placebo or changes from baseline, not differences between two active treatments [7,9,10].…”

“…FEV1 and FVC were measured at other time points. Dyspnoea was assessed by the transition dyspnoea index (TDI) total score at week 12 (o1 point is a clinically relevant change from baseline) [6,7]. Health status was assessed by St George's Respiratory Questionnaire (SGRQ) score after 12 weeks (o4 units is a clinically relevant change from baseline) [8][9][10].…”

Outcomes for COPD pharmacological trials: from lung function to biomarkers

“…In terms of the statistical frequency distributions for BDI and TDI, their ranges have been determined to be normally distributed in COPD patients [145,149,150]. They are both reproducible measures in the short (i.e.…”