Suggested minimal important differences(MIDs) of commonly used outcomes in chronic obstructive pulmonary disease (COPD) trials
| Outcome measure | Suggested MID | First author [Ref.] |
| Respiratory-specific health status and HRQoL | ||
| St George's Respiratory Questionnaire | 4 units | Jones 435 |
| Chronic Respiratory Questionnaire | 0.5 units for the average score on each domain | Schunemann 428 |
| Dyspnoea | ||
| Transition dyspnoea index | 1 unit | Mahler 436 |
| UCSD dyspnoea questionnaire | 5–7 units | Ries 437 |
| Borg scale of perceived dyspnoea | 2 units | Ries 437 |
| Visual analogue scale of dyspnoea | 10–20 units | Ries 437 |
| Lung function | ||
| Forced expired volume in one second | 100–140 mL | |
| Exercise | ||
| Maximal exercise test# | 10 W | Sutherland 438 |
| Submaximal exercise endurance test | 1.25 min | |
| 6-min walking test | 37–71 m | Wise 439 |
| Health utility | ||
| Quality of Well-Being scale | 0.03 units | Kaplan 440 |
| Feeling thermometer | 5–7 units on 100-point scale | Wouters 441 |
| Exacerbations of COPD | 1 exacerbation per yr, 22% change | Calverley 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.