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Abstract
Background There is a lack of real-world research assessing asthma management following asthma-related emergency department (ED) discharges. The objective of this study was to characterise follow-up care, healthcare resource use (HCRU) and medical costs following ED admissions in Alberta, Canada.
Methods A retrospective cohort study was conducted on adults with asthma using longitudinal population-based administrative data from Alberta Health Services. Adult patients with asthma and ≥1 ED admission from 1 April 2015 to 31 March 2020 were included. ED admissions, outpatient visits, hospitalisations and asthma-specific medication use were measured in the 30 days before and up to 90 days after each asthma-related ED admission. Mean medical costs attributable to each type of HCRU were summarised. All outcomes were stratified by patient baseline disease severity.
Results Among 128 063 patients incurring a total of 20 142 asthma-related ED visits, a substantial rate of ED readmission was observed, with 10% resulting in readmissions within 7 days and 35% within 90 days. Rates increased with baseline asthma severity. Despite recommendations for patients to be followed up with an outpatient visit within 2−7 days of ED discharge, only 6% were followed up within 7 days. The mean total medical cost per patient was $C8143 in the 30 days prior to and $C5407 in the 30 days after an ED admission.
Conclusions Despite recommendations regarding follow-up care for patients after asthma-related ED admissions, there are still low rates of outpatient follow-up visits and high ED readmission rates. New or improved multidimensional approaches must be integrated into follow-up care to optimise asthma control and prevent readmissions.
- asthma
- exacerbations
- readmissions
- administrative data
Data availability statement
Data may be obtained from a third party and are not publicly available. The data that support the findings of this study are available from Alberta Health Services (AHS). Restrictions apply to the availability of these data, which were used under license for this study. Data are available from the authors with the permission of AHS.
This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/.
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WHAT IS ALREADY KNOWN ON THIS TOPIC
There is a lack of real-world evidence assessing the impact of follow-up care after asthma-related emergency department (ED) admission on readmissions and healthcare resource use.
WHAT THIS STUDY ADDS
This study showed high rates of ED readmissions with few patients receiving follow-up care after discharge. These findings are not only indicative of the lack of asthma symptom control, but they also suggest undertreatment and/or underestimation of disease severity by physicians.
HOW THIS STUDY MIGHT AFFECT RESEARCH, PRACTICE OR POLICY
New multidimensional models of care for asthma follow-up are needed to improve postdischarge outcomes and to reduce healthcare costs. Also, this study provides a better understanding of how future therapies targeting severe exacerbations may address the clinical and economic burdens of asthma.
Introduction
Asthma is among the most common chronic conditions in Canada, affecting 4 million individuals.1 Asthma exacerbations are potentially life-threatening events in which symptoms progressively escalate, and lung function worsens to a point where urgent care may be needed. At least 65 000 asthma-related emergency department (ED) admissions occur in Canada each year.2 In Alberta, there were over 10 000 asthma-related ED admissions annually from 2011 to 2015.3 Patients with a history of an asthma-related hospital or ED admission are at increased risk of asthma-related death.4
The Global Initiative for Asthma (GINA) Global Strategy for Asthma Management and Prevention recommend that patients who are admitted to the ED for asthma exacerbation receive a follow-up appointment within 2–7 days of discharge, for reassessment of treatment and understanding of self-management strategies.4 The Health Quality Ontario asthma quality standard follows the same recommendation.5 Despite these recommendations, asthma often remains uncontrolled, and exacerbations continue to result in additional healthcare resource use (HCRU), increasing the risks for future asthma hospitalisation.6–9 An earlier study with over 115 000 asthma-related ED discharges in Alberta showed 26% of patients had repeat ED admissions during the study period (1999–2011), and 5.1% were readmitted within 30 days.10 Furthermore, only half of the patients had a follow-up visit within 30 days after discharge.10 The burden of ED admissions is substantial on the Canadian healthcare system as EDs are plagued with staffing shortages, reduced services and capacity issues.11 12 Decreasing preventable ED admissions of any aetiology is a priority to free oversubscribed emergency services and to sustain the healthcare system in Canada.
Given the potential benefits of follow-up care and education strategies post-ED discharge to reduce readmissions, there is a lack of current real-world evidence characterising if and how these interventions are implemented in clinical practice. The objective of this study is to better understand contemporary patterns of physician visits, admissions to inpatient services and ED readmissions following an asthma-related ED admission to identify opportunities for better asthma management in Canada, specifically in the province of Alberta.
Methods
Study design and patient population
This retrospective cohort study used longitudinal population-based administrative data from Alberta Health Services with individual-linked records on inpatient visits, ambulatory care and medication dispensations to allow for tracking of HCRU throughout Alberta.
The study population included all patients who were identified as having physician-diagnosed asthma using an adapted validated algorithm13; that is, if they had ≥2 ambulatory claims for asthma, ≥1 ambulatory claim for asthma with ≥2 claims for dispensation of asthma-specific medications (medications included in online supplemental table 1), or ≥1 hospital claim for asthma in a 2-year patient identification period (1 April 2013−31 March 2015) (online supplemental figure 1). Additional criteria were applied in the baseline period (1 April 2014−31 March 2015) to limit the patient population to those ≥18 years of age, with active Alberta health insurance coverage (ie, residing in Alberta since at least 1 April 2014), and without any diagnostic codes for chronic obstructive pulmonary diseases, heart failure, or cancer during the study period. Finally, patients with ≥1 ED admission during the follow-up period (1 April 2015−31 March 2020) were identified and comprised the study cohort. From the study cohort, ED admissions with asthma as the primary or secondary diagnosis were identified for the primary analyses.
Supplemental material
Outcomes and analysis
Patient demographics, disease characteristics, treatment-used and exacerbation rates were summarised for the study cohort. Exacerbations were defined as the use of oral corticosteroid (OCS) for ≥3 days, or an asthma-specific ED or hospitalisation. To minimise confounding bias due to baseline asthma severity, severity was evaluated in the baseline period (1 April 2014−31 March 2015) according to the 2015 GINA definition based on retrospective assessment of the level of pharmacotherapy treatment required to control symptoms/exacerbations.14 A detailed algorithm is documented in online supplemental table 1 outlining how patients were classified into various disease severity categories based on treatment received in the baseline year.
For the primary analyses, among the cohort of asthma-related ED admissions, all HCRU, including outpatient visits in the community and ambulatory care settings, hospitalisations, and asthma-specific prescription use, were measured in the 30 days before and up to 90 days (ie, 7 days, 15 days, 30 days, 60 days, 90 days) after each asthma-related ED admission. Readmission to the ED was also summarised in the post asthma-related ED admission period. All HCRU occurring on the same day as the ED admission were excluded from both time periods (ie, assumed to be directly connected to the index ED visit itself) to allow better comparison of the before and after ED periods. The prevalence of each type of resource utilised (ED admissions, outpatient visits, hospitalisations and dispensation of short-acting beta agonists (SABA)/OCS), for any cause, was summarised separately for the corresponding time periods of interest and further stratified by the corresponding baseline disease severity. Mean costs attributable to each type of HCRU (ie, hospitalisations, ED admissions and outpatient visits; prescription costs were excluded as they were not available) were also summarised in each corresponding time period to estimate the total all-cause medical costs incurred in respective time periods. Missing data were observed due to costs only being available for partial records from select years and facilities. For claims where costs were missing, average costs imputed from the same claim type (online supplemental table 2). All costs were inflated to 2021 CAD.
All results were stratified by baseline severity categories to allow standalone interpretation within each GINA severity group, in addition to the overall patient population. All analyses were performed with R V.4.1.1 (2021-08-10).
Results
Patient demographics
A total of 128 063 adult asthma patients with a mean (SD) age of 42.3 (15.7) years were identified (table 1; online supplemental figure 2). Among this cohort, the majority (75%, n=95 955) of patients were living in urban settings. At baseline, 55% of all patients had mild asthma (GINA 1, n=63 712; GINA 2, n=6448), 14% had moderate asthma (GINA 3, n=18 251) and 31% had severe asthma (GINA 4, n=31 552; GINA 5, n=8099). In general, the GINA 5 patients were older and had a higher comorbidity burden at index.
Patient demographics at baseline (1 April 2014 to 31 March 2015)
Asthma-related treatment
Over the follow-up period, very few patients (<1%, n=592) remained without any asthma-related pharmacological treatment. Most patients received SABAs at some point (66%, n=84 236), ranging from 32% (n=2570) among those with GINA 5 severity, to 78% (n=14 264) among those with GINA 3 severity (table 2). Among this study cohort, most patients who were using SABA were also using an inhaled corticosteroid containing product (73%, n=61 361), ranging from 30% (n=2430) among those with GINA 5 severity to 86% (n=26 998) among those with GINA 4 severity (table 2). OCS use was observed among 41% of the study cohort, ranging from 36% (n=2334) among those with GINA 2 severity to 76% (n=6155) among those with GINA 5 severity. The higher percentage of OCS use was expected due to OCS maintenance therapy being part of the algorithm for classifying patients into GINA 5 severity, where patients were assumed to be receiving maintenance therapy if the prescription was not suspected to be for treatment of an exacerbation (ie, OCS prescription was excluded if dose was ≤300 mg or duration ≤10 days) (online supplemental table 1).14 The use of other medications was low overall, with 10% (n=12 835) of the study cohort using leukotriene receptor antagonists, 2% (n=1861) for long-acting muscarinic antagonist, and <1% for biologics (n=610) and for theophylline (n=134).
Asthma-related treatment over the follow-up period (1 April 2015 to 31 March 2020)
ED admissions for asthma exacerbations
Over the follow-up period, 37% (n=47 189) of the study cohort had at least one exacerbation, with 33% (n=42 464) of the study cohort having an exacerbation that resulted in OCS use, 10% (n=12 456) of study cohort had exacerbations that required ED admission, and 2% (n=1025) of the study cohort had exacerbations that required hospitalisation (online supplemental table 3). Among the 12 456 patients with at least one ED admission with asthma as the primary or secondary diagnosis, there was an average 0.3 asthma-related ED admissions per year (online supplemental table 3), yielding approximately 1.5 ED admissions per person over the 5-year follow-up period and a total of 20 142 asthma-related ED admissions for the study population over the follow-up period (table 3; online supplemental figure 2). When stratified by baseline asthma severity, patients with GINA 1–4 severity had similar annual rates of ED admissions of 0.3 visits per patient per year. Patients with GINA 5 severity had a higher mean (SD) annual rate of 0.5 (0.9) visits. Among this subset of asthma exacerbations requiring ED admissions, 38% (n=7580) were from patients with baseline severity of GINA 1, 3% (n=673) from patients with GINA 2, 13% (n=3938) from patients with a GINA 3, 35% (n=7040) from patients with GINA 4 and 5% (n=911) from patients with GINA 5.
ED admissions for asthma exacerbations over the follow-up period (1 April 2015 to 31 March 2020)
HCRU before and after an asthma-related ED admission
ED readmissions following an asthma-related ED admission
Across baseline asthma severity categories, ED readmission rates were substantial. Approximately 10% (n=2019) of all asthma-related ED admissions were readmitted within 7 days, 20% (n=4109) by 30 days, and up to 35% (n=7014) by 90 days (figure 1; online supplemental table 4). Patients with baseline asthma severity of GINA 1 to 4 had comparable rates of ED readmission, however, ED readmission among patients of GINA 5 severity were substantially higher (26%, n=159 within 7 days; 33%, n=302 within 30 days; 49%, n=444 within 90 days).
Healthcare resource use in the 30 days before and up to 90 days after an asthma-related ED admission (n=20 142), stratified by baseline severity. ED, emergency department; GINA, Global Initiative for Asthma; OCS, oral corticosteroid; SABA, short-acting beta-agonist.
SABA and OCS use
In the 30 days before an asthma-related ED admission, 47% (n=9395) of all admissions had a SABA dispensation; compared with 29% (n=5920) within 30 days and 49% (n=9823) within 90 days postdischarge (online supplemental table 4). The rate increased with baseline GINA severity. Rates of OCS use were also higher before an asthma-related ED admission, with a rate of 39% (n=7771) in the 30 days before, compared with 18% (n=3651) by 30 days and 24% (n=4796) by 90 days postdischarge (figure 1; online supplemental table 4).
Outpatient visits
Rates of outpatient visits with a physician or specialist were higher before an asthma-related ED admission than in any time period of interest after an ED admission. Approximately 25% (n=5112) of all asthma-related ED admissions had an outpatient visit in the 30 days prior (figure 1; online supplemental table 4). However, the rate of follow-up outpatient visit to any provider-type post-ED discharge was low (6%, n=1202 within 7 days, 14%, n=2823 by 30 days and 25%, n=5078 by 90 days). Despite the rates of post-ED outpatient follow-up visits being consistently higher among patients with GINA 5 severity, only 11% (n=100) of asthma-related ED admissions were followed up within 7 days, increasing to 27% (n=245) within 30 days and 44% (n=402) within 90 days.
Hospitalisations
Rates of hospitalisations were low, with approximately 5% (n=1088) of ED admissions having a hospitalisation in the 30 days prior, and 7% (n=1323) in the 30 days after (figure 1; online supplemental table 4). Patients of GINA 5 severity consistently had higher rates of hospitalisation (11%, n=102 in the 30 days prior and 13%, n=122 in the 30 days after). Length of stay among the observed hospitalisations within the 30 days before an asthma-related ED admission was generally similar across baseline GINA severities, with a median estimate of 5 or 6 days. In the 30 days following an asthma-related ED admission, lengths of stay per hospitalisation were lower across the baseline disease severities with a median estimate of 3–4 days (online supplemental table 4).
All-cause medical costs before versus after an asthma-related ED admission
Among all visits, mean (SD) total all-cause medical costs in the 30 days prior was estimated to be $C8143 ($C42 745), with the lowest estimate of $C5176 ($C14 379) observed among admissions by patients with GINA 2 severity, and highest estimate of $C15 799 ($C28 056) among admissions by patients with GINA 5 severity (table 4). In the 30 days following an asthma-related ED admission, mean (SD) total costs were $C5407 ($C26 843) across patients of all severities, ranging from the lowest estimate of $C5172 ($C22 120) observed among admissions by patients with GINA 1 severity to the highest estimate of $C6074 ($C20 012) among admissions by patients with GINA 2 severity.
Medical costs in the 30 days before and up to 90 days after an asthma-related ED admission, stratified by baseline severity
In the subset of patients who were hospitalised, hospitalisation costs were substantial, with mean (SD) costs of $C47 108 ($C147 525) in the 30 days prior and $C20 878 ($C45 585) in the 30 days. While the outpatient costs increased with severity, as similarly observed for total cost estimates, hospitalisation costs were more variable (table 4).
Discussion
Asthma imposes considerable burden on patients in Canada largely due to asthma exacerbations, which are common and frequently result in ED admissions. The 2022 GINA recommendations emphasise the importance of managing exacerbations and providing adequate follow-up care after an exacerbation.4 Real-world research can help to better understand how interventions are implemented and identify opportunities for improving postdischarge care to prevent and reduce asthma exacerbations that result in increased HCRU.
This study used longitudinal population-based administrative data consisting of over 128 000 adult patients with 5 years of follow-up to evaluate patterns of physician visits, admissions,= and readmissions in patients with asthma-related ED admissions. High rates of ED readmission were observed, with 10% resulting in readmissions within 7 days and 35% within 90 days of initial admission. Rates were considerably higher for patients with greater baseline asthma severity, with almost twice the rate of ED readmissions among GINA 5 patients compared with patients of other baseline disease severities. While patients with greater asthma severity were more likely to have ED readmissions, patients with mild asthma (GINA 1 and 2) accounted for 40% of all asthma-related ED admissions over the study period. This estimate, which aligns with published literature,15 shows that there has been little improvement post-discharge care for asthma over recent years. In addition, patients with baseline GINA 1 severity did not have the lowest rates of HCRU but had higher rates of hospitalisation and ED admissions compared with those with GINA 2 or 3 severity, which is indicative of probable undertreatment. As GINA severity categorisation is based on the level of treatment required to control asthma symptoms, these results suggest that severity of patients as assessed by treating physicians is markedly underestimated.
This study highlights the need for more effective strategies to prevent asthma-related ED admissions. OCS use before an asthma-related ED admission was observed among 40% of admissions, likely indicative of self-management at the onset of exacerbation symptoms, thereby indicating a need and opportunity for optimisation of current treatment and improvement in self-management planning. Similarly, SABA dispensation was common before an asthma-related ED admission, suggesting a potential need to assess current treatment and presence of SABA overuse. This is particularly important in this population, as SABA overuse is associated with increased exacerbations.12 16–18 It should also be noted that the use of biological therapies was infrequent overall, even among patients with GINA 5 severity at baseline, signifying potential inadequate control of the patient’s disease and the need for reassessment of current treatment regimen. Lastly, the observed presence of hospitalisations before ED admissions suggests room for improved discharge planning and follow-up for patients after they are hospitalisation.
The results of this study also suggest opportunities for improving care for patients after they have been admitted to the ED. Despite recommendations for patients to be followed up within 2–7 days of discharge,4 only 6% of ED admissions had an outpatient visit within 7 days, increasing to only 14% by 30 days and 25% by 90 days. It is important to note that a previous population-based study by Rowe et al19 using administrative data from Alberta observed a lower rate of ED readmission of <10% within 30 days and a much higher rate of follow-up of 30%–45% within 7 days and 50%–80% within 30 days postdischarge from the ED.19 Additional research is needed to elucidate the cause(s) in the significant reduction of the follow-up visit with the primary care provider, as this understanding could potentially help reduce ED readmissions. This is particularly alarming given the abundance of evidence demonstrating improved clinical outcomes and reduced HCRU when asthma patients receive appropriate follow-up care following asthma-related ED admissions.20–24 Lastly, given that 10% of all asthma-related ED admissions resulted in hospitalisations within 90 days of discharge from the ED, and the known association between ED admissions and future hospitalisations,6 25 26 this would be an additional factor to consider to improve patient management.
Previous studies have shown that successful asthma educational programmes among patients previously hospitalised for asthma exacerbations resulted in reduced readmissions, less absenteeism from school/work, and lower costs associated with HCRU.22 27 28 While the cost per ED admission has been reported to be around $C300 in Canada in 2018−2019,29 this study found significant healthcare costs associated with the time periods both before and after an asthma-related ED admission regardless of baseline asthma severity. Overall, the mean total medical costs in the 30 days prior and in the 30 days after an ED admission were approximately $C14 000. These costs were incurred due to any outpatient or inpatient services for any cause within these time periods. From a societal perspective, based on a total of 20 142 asthma-related ED admissions over a period of 5 years, this translates into a cost burden of approximately $C282 million or an average of $C56 million per year. It is also important to note that among those who end up hospitalised after their asthma-related ED admission, the costs are approximately four times that of the costs estimated for those with at least one follow-up outpatient visits. As a result, it is essential, also from an economic perspective, to promote follow-up visits in the interest of preventing future hospitalisations and reducing the healthcare resource burden.
The strengths of this study derive from the use of a population-based dataset from Alberta, which covers a large population and are representative of a diverse set of adults with asthma. The study population was constructed based on a validated definition for identifying adults with asthma in health administrative databases,13 minimising risk of misclassification of the cohort. In addition, the low attrition rate observed in this study minimises risk of misclassification of outcome from unobserved data. Furthermore, the claims dataset used for this analysis comprehensively captured all services provided and medications dispensed, thus increasing confidence in capture of HCRU. However, the costs in this study were not as comprehensively captured. Prescription dispensations were not available, and for medical costs, only costs from select urban facilities in Calgary and Edmonton were available. While most of the cohort was from urban settings, the magnitude of the impact of the missing costs on the overall estimates remains unclear. Furthermore, as costs were imputed, the costs may be over-represented for some facilities and under-represented for others. As a result, while the exact costs may not be reflective of the total costs of treatment in the time periods around a severe asthma exacerbation, HCRU in the respective time periods also suggest that costs of an episode of severe asthma exacerbation may extend beyond just the emergency visit. Several other limitations of this study stem from the reliance of the GINA algorithm on dispensed prescription medication data at baseline. First, it is important to note that the dispensation of asthma-related treatments within the baseline period informed a patient’s baseline severity, as a result, findings of medication use over the follow-up are likely also associated with baseline dispensation patterns. Second, while the GINA algorithm is aligned with clinical guidelines at the time of the index date,30 the lack of clinical information in the available data to assess control (eg, patient reported or otherwise mentioned frequency of symptoms) or severity (eg, laboratory measured levels of blood eosinophils), leaves room for potential misclassification, particularly when actual use of the dispensed medications cannot be assessed. For example, among patients defined to have GINA 5 severity at baseline, while the definition used to define maintenance OCS of >300 mg or with duration of >10 days duration is based on the relevant clinical guidelines within the baseline period,30 it is not possible to assess the dose and how frequently the patients were actually using the dispensed OCS, and this could have led to inclusion of patients of lower severity in the GINA 5 group and potential for underestimation of HCRU and costs within this group. Third, asthma severity is determined at baseline, prior to the study period. Given that the majority of patients had 5 years of follow-up, it is possible that the severity classification at baseline is likely an underestimate of patients within more severe GINA steps at the time of the exacerbation that resulted in asthma-related ED admission. As a result, the findings of HCRU and costs can be potentially overestimated for the GINA steps of lower severity. Nevertheless, because the GINA algorithm is reliant on dispensed prescription medication, and given the dynamic nature of asthma as well as guideline changes throughout the study period, standardising the time period used to determine GINA steps across all patients and within the same calendar time period is anticipated to have decreased the overall level of potential bias in this study, especially when taking into account potential impact of seasonality and other environmental factors, such as influenza or forest-fire seasons. Lastly, a potential limitation of this study includes the potentially limited generalisability of the findings from the province of Alberta to the rest of Canada, or a wider patient population. Due to the differences in clinical practice, patient population and environmental factors as mentioned above, it is important to keep these factors in mind when interpreting the findings of this study beyond the study settings.
In conclusion, this study showed that little progress has been made over the past decade in providing effective follow-up care after asthma-related ED admissions and reducing readmissions. Less than 10% of asthma-related ED admissions were followed by outpatient visits within 7 days while ED readmission rates were nearly 25% after 30 days. The implications of these findings include the acknowledgement that new models of care for asthma follow-up are needed. These may include pharmacist-directed care, direct referral to asthma educators and/or direct referral to asthma specialty clinics. Recognition that an ED admission is a failure of asthma therapy may also lead to earlier evaluation for the need of both maintenance treatment optimisation and biological therapies in these high-risk patients. Patients are unable to optimise asthma control and prevent readmissions In addition, the results of this study provide an important benchmark for contemporary HCRU estimates in patients who experience severe exacerbations in Alberta, Canada, allowing for a better understanding of how future therapies targeting severe exacerbation may address not just the clinical burden of asthma but the economic burden as well.
Data availability statement
Data may be obtained from a third party and are not publicly available. The data that support the findings of this study are available from Alberta Health Services (AHS). Restrictions apply to the availability of these data, which were used under license for this study. Data are available from the authors with the permission of AHS.
Ethics statements
Patient consent for publication
Ethics approval
Ethics approval was obtained from the University of Alberta’s Research Ethics Board (Study ID #MS4_Pro00094829).
References
Supplementary materials
Supplementary Data
This web only file has been produced by the BMJ Publishing Group from an electronic file supplied by the author(s) and has not been edited for content.
Footnotes
Contributors All authors contributed to the study conception and design. Data analysis was performed by CQ and PJ. All authors contributed to the writing of the manuscript. All authors read and approved the final manuscript. IM is the guarantor of the study and accepts full responsibility for the work and/or the conduct of the study, had access to the data, and controlled the decision to publish.
Funding This study was funded by AstraZeneca Canada, Inc. (Grant number: n/a)
Competing interests IM has received advisory board and speaker’s honoraria from AstraZeneca, Sanofi and Boehinger-Ingelhiem, and research grants from Boehringer-Ingelheim and AstraZeneca. AR and MT are employees of AstraZeneca Canada. MS is a former employee of AstraZeneca Canada. CQ, PJ and JK are employees of Broadstreet HEOR which was contracted by AstraZeneca Canada for the conduct of this study. MB has received advisory board and speaker’s honoraria from AstraZeneca, GSK, Pfizer, Sanofi, Grifols, Covis and grants and funding for clinical trials from CIHR, AI, AstraZeneca, GSK, Mereo Pharm, BI, Alberta Lung Association. His affiliations are as follows: Canadian Thoracic Society Executive Committee, Past Co-Chair of the CTS COPD Clinical Assembly, Co-Chair of the Royal College of Physicians and Surgeons Adult Respiratory Examination.
Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.
Provenance and peer review Not commissioned; externally peer reviewed.
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