Ekström M; Department of Clinical Sciences Lund,Faculty of Medicine, Lund University, Lund, Sweden.
Lewthwaite H; Li PZ; Bourbeau J; Tan WC; Jensen D; Montréal, QC,

Chest [Chest] 2024 Oct 28.
Date of Electronic Publication: 2024 Oct 28.

Background: COPD management is guided by the respiratory symptom burden, assessed using the modified Medical Research Council (mMRC) scale, the COPD Assessment Test (CAT), or both.
Research Question: What are the abilities of mMRC and CAT to detect abnormally high exertional breathlessness on incremental cardiopulmonary cycle exercise testing (CPET) in people with COPD?
Study Design and Methods: Analysis of people ≥ 40 years of age with FEV ₁ to FVC ratio of < 0.70 after bronchodilator administration and ≥ 10 pack-years of smoking from the Canadian Cohort Obstructive Lung Disease study. Abnormal exertional breathlessness was defined as a breathlessness (Borg scale 0-10) intensity rating more than the upper limit of normal at the symptom-limited peak of CPET using normative reference equations.
Results: We included 318 people with COPD (40% women) with a mean (SD) age of 66.5 (9.3) years and FEV ₁ of 79.5% predicted (19.0% predicted); 26% showed abnormally low exercise capacity (peak oxygen uptake less than the lower limit of normal). Abnormally high exertional breathlessness was present in 24%, including 9% and 11% of people with mMRC score of 0 and CAT score of < 10, respectively. An mMRC score of ≥ 2 and CAT score of ≥ 10 was most specific (95%) to detect abnormal exertional breathlessness, but showed low sensitivity of only 12%. Accuracy for all scale cutoffs or combinations was < 65%. Compared with people with true-negatives findings, people with abnormal exertional breathlessness but low mMRC score, low CAT scores (false-negatives findings), or both showed worse self-reported and physiologic outcomes during CPET, were more likely to have physician-diagnosed COPD, but were not more likely to be taking any respiratory medication (37% vs 30%; mean difference, 6.1%; 95% CI, -7.2 to 19.4; P= .36).
Interpretation: In COPD, mMRC and CAT show low concordance with CPET and fail to identify many people with abnormally high exertional breathlessness.
Clinical Trial Registry: ClinicalTrials.gov; No.: NCT00920348; URL: www.
Clinicaltrials: gov.
Competing Interests: Financial/Nonfinancial Disclosures The authors have reported to CHEST the following: J. B. and W. C. T. report receiving institutional funding for the CanCOLD study from Astra Zeneca Canada, Ltd., Boehringer-Ingelheim Canada, Ltd., GlaxoSmithKline Canada, Ltd., Merck, Novartis Pharma Canada, Inc., as well as Nycomed Canada, Inc. (W. C. T.), Pfizer Canada, Ltd. (W. C. T.), Trudell (J. B.), and Grifolds (J. B.). M. E. declares no conflicts of interest related to this work. Unrelated to this work, M. E. has received a research grant from ResMed and personal fees from AstraZeneca, Boehringer Ingelheim, Novartis, and Roche. None declared (M. E., H. L., P. Z. L., D. J.).