Table 4—

Suggested minimal important differences(MIDs) of commonly used outcomes in chronic obstructive pulmonary disease (COPD) trials

Outcome measureSuggested MIDFirst author [Ref.]
Respiratory-specific health status and HRQoL
 St George's Respiratory Questionnaire4 unitsJones 435
 Chronic Respiratory Questionnaire0.5 units for the average score on each domainSchunemann 428
 Transition dyspnoea index1 unitMahler 436
 UCSD dyspnoea questionnaire5–7 unitsRies 437
 Borg scale of perceived dyspnoea2 unitsRies 437
 Visual analogue scale of dyspnoea10–20 unitsRies 437
Lung function
 Forced expired volume in one second100–140 mL
 Maximal exercise test#10 WSutherland 438
 Submaximal exercise endurance test1.25 min
 6-min walking test37–71 mWise 439
Health utility
 Quality of Well-Being scale0.03 unitsKaplan 440
Feeling thermometer5–7 units on 100-point scaleWouters 441
Exacerbations of COPD1 exacerbation per yr, 22% changeCalverley 442
  • These values are provided for informational purposes and should be considered estimates with tolerance levels rather than definite cut-off values. HRQoL: health-related quality of life; UCSD: University of California, San Diego. #: in the context of lung volume reduction surgery as an intervention. Modified from 443.