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‘Exacerbation-free time’ to assess the impact of exacerbations in patients with chronic obstructive pulmonary disease (COPD): a prospective observational study

Lonneke M Boer, Erik W Bischoff, Xandra Borgijink, et al.
npj Prim Care Respir Med 2018;28:12

Exacerbation frequency is a frequently used indicator in chronic obstructive pulmonary disease (COPD) studies. However, this may not fairly reflect the effects of every intervention. For example, self-management strategies are often not intended to prevent exacerbations occurring, but to reduce their severity. Boer and colleagues from Nijmegen in the Netherlands therefore propose considering the total amount of time a patient suffers from exacerbations, rather than the simple frequency.

This study was a secondary analysis of two prospective cohort studies, one in primary care and one in an outpatient setting. Data from 166 patients was included. In patients with <3 exacerbations per year, the correlation between exacerbation frequency and exacerbation-free time was strong, but this was not the case for those with ≥3 exacerbations per year.

Medical Research Council (MRC) category was related to exacerbation frequency, and to some extent exacerbation-free time. Patients in MRC category 1 had more exacerbation-free time than those in category 3, but there was no significant difference between patients in categories 2 and 3. Current smokers also had less exacerbation-free time, but not a higher exacerbation frequency, than ex-smokers or never-smokers. Correlation between exacerbation frequency and health-related quality of life scores was weak. However, greater exacerbation-free time was related to a higher quality of life score.

This suggests that exacerbation-free time and exacerbation frequency are two distinct indicators in COPD, particularly in smokers and frequent exacerbators. The greater correlation of exacerbation-free time with quality of life may indicate this is a more patient-centred outcome than exacerbation frequency, which has relevance for clinical practice as well as research.

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