Identifying Abnormal Exertional Breathlessness in COPD
Magnus Ekström, Hayley Lewthwaite, Pei Zhi Li, Jean Bourbeau, Wan C. Tan, Dennis Jensen, J. Mark FitzGerald, Don D. Sin, Darcy D. Marciniuk, Denis E. O’Donnell, Paul Hernandez, Kenneth R. Chapman, Brandie Walker, Shawn Aaron, François Maltais, Jonathon Samet, Milo Puhan, Qutayba Hamid, James C. Hogg, Dany Doiron, Palmina Mancino, Pei Zhi Li, Dennis Jensen, Carolyn Baglole, Yvan Fortier, Don Sin, Julia Yang, Jeremy Road, Joe Comeau, Adrian Png, Kyle Johnson, Harvey Coxson, Jonathon Leipsic, Cameron Hague, Miranda Kirby, Mohsen Sadatsafavi, Teresa To, Andrea Gershon, Zhi Song, Andrea Benedetti, Dennis Jensen, Yvan Fortier, Miranda Kirby, Christine Lo, Sarah Cheng, Elena Un, Cynthia Fung, Wen Tiang Wang, Liyun Zheng, Faize Faroon, Olga Radivojevic, Sally Chung, Carl Zou, Palmina Mancino, Jacinthe Baril, Laura Labonte, Kenneth Chapman, Patricia McClean, Nadeen Audisho, Brandie Walker, Curtis Dumonceaux, Lisette Machado, Paul Hernandez, Scott Fulton, Kristen Osterling, Denise Wigerius, Shawn Aaron, Kathy Vandemheen, Gay Pratt, Amanda Bergeron, Denis O’Donnell, Matthew McNeil, Kate Whelan, François Maltais, Cynthia Brouillard, Darcy Marciniuk, Ron Clemens, Janet Baran, Candice Leuschen
Abstract
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: 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: 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 showed low concordance with CPET and failed to identify many people with abnormally high exertional breathlessness. CLINICAL TRIAL REGISTRY: ClinicalTrials.gov; No.: NCT00920348; URL: www. CLINICALTRIALS: gov.