A clinical trial’s inclusion criteria or endpoint may use the modified Medical Research Council (mMRC) dyspnoea scale (a measure of the degree of dyspnea), which was suggested by recommendations. In any investigations, the category descriptions had not been validated against the dyspnoea severity grade.
The researchers evaluated the content validity of the mMRC scale among 16 individuals (13 with cardiac/respiratory illness) using cognitive interviews (the Think Aloud method). To attain representation across a range of demographic characteristics, participants were recruited. Participants were asked to score the phrases “in order from the best breathing to the worst breathing” after being shown all 5 mMRC descriptors on screen in random order during remote video interviews.
Participants’ average age was 57 years (range 22–84 years). In addition to COPD, asthma, lung cancer, lung infection, interstitial lung disease, heart failure, depression, and anxiety, 11 people had multimorbidity (≥2 comorbidities). The duration of breathlessness ranged from 2 weeks to >25 years. The median rank of the grade descriptors for mMRC grades 0, 1, and 4 were consistent but not for grades 2 and 3. However, there was a significant variation in the results for mMRC grade 0.
In particular, for grades 0, 2, and 3, the study discovered significant variation in participant grading of the mMRC descriptors, suggesting that the mMRC may not be a suitable discriminator of change or difference in dyspnoea severity. The results of the study showed how crucial content validation was, especially for established PROs like mMRC.