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Original Research: Obstructive Lung Diseases |

Ten-Year Trends in Direct Costs of COPDTen-Year Trends in Direct Costs of COPD: A Population-Based Study FREE TO VIEW

Amir Khakban, MSc; Don D. Sin, MD, MPH; J. Mark FitzGerald, MD; Raymond Ng, PhD; Zafar Zafari, MSc; Bruce McManus, MD, PhD; Zsuzsanna Hollander, PhD; Carlo A. Marra, PharmD, PhD; Mohsen Sadatsafavi, MD, PhD
Author and Funding Information

From the Collaboration for Outcomes Research and Evaluation (Mr Khakban), Faculty of Pharmaceutical Sciences, Institute for Heart + Lung Health (Drs Sin, FitzGerald, and Sadatsafavi), Department of Medicine, Respiratory Division, and the Centre for Clinical Epidemiology and Evaluation (Mr Zafari and Dr Sadatsafavi), the University of British Columbia, Vancouver, BC; Institute for Heart + Lung Health (Drs Ng, McManus, and Hollander), Center of Excellence for Prevention of Organ Failure (PROOF Centre), Vancouver, BC; and School of Pharmacy (Dr Marra), Memorial University of Newfoundland, St. John’s, NF, Canada.

CORRESPONDENCE TO: Mohsen Sadatsafavi, MD, PhD, Centre for Clinical Epidemiology and Evaluation, 7th Floor, 828 W 10th Ave, Research Pavilion, Vancouver, BC, V5Z 1M9, Canada; e-mail: msafavi@mail.ubc.ca


FUNDING/SUPPORT: This study was supported by the Institute for Heart + Lung Health, the University of British Columbia. Mr Khakban receives salary support from Genome Canada: Genome British Columbia, Providence, St. Paul’s Hospital Foundation, and PROOF Centre. Dr Sadatsafavi receives salary support from the National Sanitarium Association and is also supported by the Early Research Leaders Initiative from the Canadian Respiratory Research Network. Dr Sin is a Tier 1 Canada Research Chair in COPD.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details.


Chest. 2015;148(3):640-646. doi:10.1378/chest.15-0721
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BACKGROUND:  Up-to-date estimates of burden of diseases are required for evidence-based decision-making. The objectives of this study were to determine the excess costs of COPD and its trend from 2001 to 2010 in British Columbia, Canada.

METHODS:  We used British Columbia’s administrative health data to construct a cohort of patients with COPD and a matched comparison cohort of subjects without COPD. We followed each patient from the time of first COPD-related health-care event (or equivalent time for the comparison cohort). Direct medical costs (in 2010 Canadian dollars [$]) were calculated based on billing records pertaining to hospital admissions, outpatient services use, medication dispensations, and community care services. We determined the excess medical costs of COPD by calculating the difference in overall medical costs between the COPD and the comparison cohorts.

RESULTS:  The COPD and comparison cohorts comprised 153,570 and 246,801 people, respectively (for both cohorts, mean age at entry was 66.9 years; 47.2% female patients). The excess costs of COPD during the study period were $5,452 per patient-year. Inpatient, outpatient, medication, and community care costs were responsible for 57%, 16%, 22%, and 5% of the excess costs, respectively. Excess costs increased by $296/person-y (P < .01), with hospital costs demonstrating the largest increase over time ($258/person-y; P < .01).

CONCLUSIONS:  The direct economic burden of COPD is high and has increased significantly between 2001 and 2010 over and above the increase in the health-care costs of the general population. Further investigation is required to elucidate the underlying reasons for the temporal increase in COPD direct costs.

Figures in this Article

COPD is a common disorder affecting > 200 million patients worldwide.1 In many jurisdictions, including Canada, COPD is the leading cause of medical hospitalization,2 mainly attributable to episodes of increased disease activity, or “exacerbations.”3 Exacerbations are associated with significant morbidity, with severe exacerbations often requiring hospital admissions or even intensive care support.4 In many patients, the diagnosis of COPD is first made during an exacerbation episode, requiring an urgent physician visit or hospitalization.5

The burden of COPD is a complex function of its prevalence, environmental and behavioral factors, availability and use of treatment options, as well as real-world practice patterns. In this dynamic setting, up-to-date cost estimates are required for evidence-informed decision-making. Although the direct economic impact of COPD in Canada has been assessed previously,2 this evaluation occurred more than a decade ago and its relevance today is uncertain.

Our primary objective in this study was to estimate the excess direct costs related to the care of patients with physician-diagnosed COPD from 2001 to 2010 in British Columbia. The secondary objectives were to evaluate the relative contributions of the various cost components (inpatient, outpatient, medication, and community care) to the excess costs and to compare the trends of costs over time and across sex and age groups. Finally, we compared the differences in excess costs over time between individuals whose COPD was diagnosed in an outpatient setting with those who were diagnosed during a COPD-related hospitalization.

Data Sources

Canada’s public health-care system includes universal health-care coverage of all residents, with no copayments for hospitalization or outpatient encounters for any surgical or medical specialty. British Columbia is the third largest Canadian province with 4.4 million people (as of 2011).6 The administrative needs of British Columbia’s health-care system have resulted in creation of centralized databases that comprehensively capture health-care use, including hospitalizations, physician encounters, and medications for all legal residents, regardless of age, immigration status, or coverage by third-party insurers. For this study, we used these data from 1996 to 2012. We merged the following databases together: a vital statistics database, which contains birth and death records7; a registration database, which contains the date of registration with the health-care system8; the Medical Services Plan database, which contains information on every outpatient health-service encounter including physician visits9; the Discharge Abstract Database, which includes records of all hospital separations10; the Continuing Care database, which captures home and community care services11; and the PharmaNET database, which contains records of all medications dispensed at pharmacies in the province.12 Ethics approval was obtained from the University of British Columbia’s institutional review board (University of British Columbia Human Ethics Board No. H13-00684). All inferences, opinions, and conclusions drawn in this research are those of the authors, and do not reflect the opinions or policies of the Data Steward(s).

Study Population

From the merged database, we created a cohort of patients with COPD by applying a validated case definition of COPD.13 Patients were deemed to have COPD if they were ≥ 35 years of age and had at least one COPD-related hospitalization (using International Classification of Diseases, Ninth Revision or International Classification of Diseases, 10th Revision, codes for COPD anywhere in the list of discharged diagnoses) or three or more COPD-related outpatient visits over a rolling 24-month window. COPD codes were defined using the International Classification of Diseases, Ninth Revision codes 491, 492, 493.2x, 496 or International Classification of Diseases, 10th Revision codes J41, J42, J43, and J44. This case definition has a specificity of 95.4% for identifying patients with COPD.13 For each person in the COPD cohort, we requested data of up to two people from the general non-COPD population matched with respect to sex, birth year, local health-delivery area, and the neighborhood income (in quintiles).

Study Period and Follow-up Time

We considered the first 5 years of the available data (1996-2000) as a “wash-in” period to allow sufficient time for patients to experience a COPD-related health-service use, and to enable us to detect incident COPD cases for secondary analyses.14 We also did not include the last 2 years (2011, 2012), as the 2-year time window for case definition would result in incomplete identification of incident cases in this period. As such, the study period was from January 1, 2001, to December 31, 2010.

The first date of any record in the data for each patient within the study period was considered the entry date. Among patients who satisfied the case definition of COPD, we identified the date of the patient’s first health-care encounter after entry for which the principal diagnosis was COPD.14 This date was defined as the “index date.” For the individuals in the comparison cohort, we chose as the index date the same day of follow-up (since entry date) as their matched patient with COPD. The start of follow-up period (time zero) was the index date and follow-up ended at the date of death, end of study period, or last date of any resource use, whichever came first.

Resource Use and Costs

Total direct costs for each patient were calculated by adding the costs of hospitalizations, outpatient services, medication dispensations, and community care services. For hospitalizations, we used the case-mix methodology15: Each hospitalization record is accompanied by a resource intensity weight (RIW), a relative measure of intensity of resource use.16 An RIW value of 1 indicates that the hospitalization in question consumed an average amount of resources compared with all hospitalizations occurring in the same fiscal year within British Columbia. Accordingly, multiplication of the RIW value of the hospitalization by the average hospitalization costs (obtained from the Canadian Institute for Health Information) for that fiscal year provided an estimate of the costs of hospitalization. For all other cost components, cost information was directly available from the billing records. All costs were converted to year 2010 Canadian dollars ($) using the Consumer Price Index by applying the medicinal and pharmaceutical index of for medication cost and health-care index for other costs.17

Statistical Analysis

All analyses were performed using SAS Enterprise, version 6.1 (SAS Institute Inc). P values (two-tailed) were considered significant at the .05 level. Excess costs overall and within-cost components were estimated by fitting regression models with total costs within each year as the dependent variable and cohort membership (COPD cohort = 1, comparison cohort = 0), calendar time, age group at index date, and sex as independent variables. The regression coefficient for cohort membership represents adjusted excess costs between the COPD and comparison groups. To test for trend, we fitted the same model with the addition of an interaction term between cohort membership and calendar year; the regression coefficient captures the time trend for the excess costs. The same framework also allowed us to evaluate the relation between age group, sex, and excess costs. We used generalized linear models, with identity link function and normal distribution, with generalized estimating equations to account for the clustered nature of the data (several costs-per-year values within each study subject).

To compare resource use between those whose COPD was first diagnosed in inpatient or outpatient settings, we created a subcohort of incident cases within the COPD cohort as those who had at least 3 years of data without any COPD-related diagnosis before their first COPD-related resource use. COPD was considered as an “inpatient-first” diagnosis if the first COPD-related diagnostic code was from a hospitalization record with COPD as the most responsible discharge diagnosis. Similarly, COPD was considered as an “outpatient-first” diagnosis if the first COPD-related diagnostic code was found in an outpatient setting. The excess costs between the two groups were calculated for each month since diagnosis.

Sensitivity Analyses

The definition of the index date in this design guarantees that patients in the COPD cohort had resource use records on their first day of follow-up; this is not necessarily the case for the comparison cohort. To address concerns that this might result in an upward bias in estimating the excess costs of COPD, we performed sensitivity analyses by calculating excess costs after removing the first month of follow-up, as well as the first 6 months of follow-up.

Population Characteristics

A total of 153,570 patients satisfied the case definition of COPD. These patients were matched to 246,801 people from the general population without COPD (comparison cohort). Table 1 provides the baseline characteristics of study subjects at their index date. Mean follow-up time was 5.4 and 5.5 years for individuals in the COPD and comparison cohorts, respectively.

Table Graphic Jump Location
TABLE 1 ]  Baseline Characteristics of the COPD and Comparison Cohorts

Figure 1 demonstrates the trend in the number of COPD cases (satisfying the case definition criteria) and excess costs over time. The number of patients who satisfied the case definition increased over time from 59,091 in 2001 to 98,368 in 2010. This corresponds to a prevalence of 2.6% in 2001 and 3.8% in 2010, with an annual increase of 0.11% (3.8% per year relative to 2001 prevalence, P < .01).

Figure Jump LinkFigure 1 –  Number of patients with, and annual excess costs (total and by component) of, COPD, 2001 through 2010. All costs are in CAD. CAD = Canadian dollars.Grahic Jump Location
Excess Costs of COPD and Their Trend

On average, the total direct medical costs for a patient in the COPD cohort were $8,600/y (95% CI, $8,546-$8,655). This value was $3,148/y (95% CI, $3,126-$3,171) for subjects in the comparison cohort. The adjusted excess costs of COPD were $5,452/y (95% CI, $5,393-$5,510). The excess costs related to the care of patients with COPD increased over time by $296/y per patient (P < .01). Excess costs during the first 5 years of the study period (2001-2005) were $4,493, compared with $6,160 in the final 5 years (2006-2010).

Excess Costs and Their Trend by Cost Components

Costs related to hospital admissions were the largest driver of the total excess costs, at $3,090/y (56.7% of total excess costs). The second largest component was the costs of medications ($1,184/y; 21.7%), followed by costs of outpatient services ($903/y; 16.6%). Community care services were responsible for $275/y (5%) of the excess costs. Excess costs increased by $296/person-y (P < .01). Within cost categories, inpatient care demonstrated the largest increase over time, by $258/y per patient (P < .01). Outpatient and medication costs increased by $16 (P < .01) and $45 (P < .01) per patient-year, respectively. Conversely, community care costs decreased by $26 per patient-year (P < .01) (Fig 1).

Excess Costs of COPD by Sex and Age Group

Figure 2 illustrates excess costs by sex and age groups. Excess costs increased with increasing age from $4,468/y among patients 35 to 44 years of age to $6,720/y in people ≥ 85 years of age. Costs were higher among women compared with men in all age categories except for those who were 55 to 64 years of age.

Figure Jump LinkFigure 2 –  A, B, Excess costs of COPD in different sex and age groups. All costs are in 2010 CAD. A, Excess costs in total. B, Excess costs by cost components. See Figure 1 legend for expansion of abbreviation.Grahic Jump Location
Sensitivity Analyses

Results only slightly changed in the sensitivity analyses. Removing the first month after the index date decreased the estimate of the annual excess costs to $4,766 per person and the annual change to $275 per person. Costs related to hospital admissions remained the largest component (51.9%). Removing the first 6 months resulted in an estimate of $4,623 in annual per-person excess costs and an annual rate of change of $277 per person.

Excess Costs in the Incident COPD Cohort

A total of 105,846 people satisfied the incident case definition of COPD from 2001 to 2010. Among them, 59,616 (56.3%) were outpatient-first and 46,230 (43.7%) were inpatient-first cases. Figure 3 provides the trend in monthly excess costs of COPD from the incident date. There was a sharp initial spike in excess costs, which rapidly declined after 3 months to a plateau value of approximately $410/mo ($4,920/y). Hospitalization costs were the main driver of the initial spike, contributing to 85% of the costs in the first 3 months. The initial spike in COPD excess costs was only visible in the inpatient-first group. However, the inpatient-first group accrued higher excess costs along the entire follow-up period (Fig 4).

Figure Jump LinkFigure 3 –  A, B, Monthly excess costs of COPD from index date. All costs are in 2010 CAD. A, Excess costs in total. The first month is excluded from this graph because of its very high total cost value ($5,424). B, Excess costs by relative contribution of cost components. See Figure 1 legend for expansion of abbreviation.Grahic Jump Location
Figure Jump LinkFigure 4 –  Monthly excess costs of COPD according to the initial diagnosis condition. All costs are in 2010 CAD. The first month is excluded from this graph because of its very high value of inpatient-first cost ($12,372). See Figure 1 legend for expansion of abbreviation.Grahic Jump Location

The main goal of this study was to estimate the excess direct costs of diagnosed COPD cases and their trend over time. We found that the average annual excess cost of COPD was $5,452 per patient. On average, patients with COPD incurred 2.73 times higher direct medical costs than subjects in the non-COPD cohort (who might already have other health conditions given their average age of 66.6 years); this shows the devastating economic burden of COPD in terms of only its direct medical costs. The main attributable factor for the excess costs was hospitalization, accounting for 60% of the total excess costs. Our findings are in-line with results of previous studies,18 in which costs of hospitalization contributed to > 50% of all direct costs.2 Worryingly, the excess costs of COPD rapidly increased in the 10-year time period, being 38% higher in 2010 than in 2001. Combining the number of individuals detected as having COPD in our dataset with per-patient estimates of excess costs results in an overall excess cost of COPD of $600 million in British Columbia in 2010 alone. Of note, this is likely an underestimate, given that the specific case definition used to construct the COPD cohort inevitably excludes many COPD cases.

Our study updates some of the old estimates of the economic burden of COPD in Canada.2 To our knowledge, our study is the first to provide insight into the short- and long-term cost trends in patients whose COPD was diagnosed during an episode of hospital admission (likely due to COPD exacerbation). A large fraction of incident cases in our study sample (43.7%) had no record of COPD-related diagnostic codes in at least 3 years before an episode of COPD-related inpatient care. Predictably, these patients incurred large initial costs. However, the long-term costs of disease for such patients remained higher than the rest of COPD cases. While this difference shall not be interpreted causally (eg, the inpatient-first incident cases might have more severe COPD), it provides insight into the future burden of COPD according to the initial diagnostic context.

The main strength of our study is its longitudinal design based on access to the data of all the residents of a well-defined geographic area over 17 years. We had detailed information on all medical resource use, including medications, outpatient services, and hospital-based and community care. We also had access to the data of a random sample of comparison subjects, which allowed us to determine with precision the excess costs of COPD. By subtracting the “background” level of health-care resource use, the calculation of excess costs properly removes the secular cost trends and takes into account the burden of comorbid conditions according to their relative prevalence in COPD and the extent they affect health-care resource use.

One limitation of our study was that the diagnosis of COPD was based on billing medical records. This may have led to possible diagnostic misclassifications. Our deliberate choice of COPD case-definition criteria with high specificity was to minimize this misclassification bias. However, the trade-off between sensitivity and specificity means not all diagnosed COPD cases in the target population have been captured (this is reflected in lower estimates of prevalence in this cohort than the reported prevalence of COPD). The database we used did not capture information on lung function or smoking. Thus, we could not determine the costs according to disease severity or smoking status. In addition, not all components of direct costs are captured in the administrative health data. For example, costs of nonprescription medication or devices, and costs of complementary and alternative care are not captured in our results.

In conclusion, our findings highlight several important public health concerns in COPD. These results indicate a major increase in the overall burden of COPD in the span of a decade. Despite improvements, current disease management and care standards seem to be far from optimal and are not likely making any major impact. This is especially evident in the high and growing rate of hospitalization as a major determinant of the burden of COPD. More than 40% of patients were diagnosed after hospital admission. This observation is consistent with, and is an expected consequence of, low rates of spirometry use in the community and limited awareness of COPD among general practitioners.19 The concerning trends observed in this study will not change without systematic and coordinated attempts that target the entire pathway of COPD care from risk-factor modification to early diagnosis and better disease management.

Author contributions: D. D. S. and M. S. had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis. A. K. served as principal author. A. K., D. D. S., J. M. F., and M. S. conceived the study idea; A. K. and M. S. designed the experiments; D. D. S., J. M. F., Z. H., and M. S. acquired the data; A. K. and M. S. contributed to statistical analysis; R. N., B. M., and C. A. M. contributed to data interpretation; A. K. wrote the first draft of the manuscript; A. K., D. D. S., J. M. F., R. N., Z. Z., B. M., Z. H., C. A. M., and M. S. critically commented on the manuscript and approved its final version.

Financial/nonfinancial disclosures: The authors have reported to CHEST the following conflicts of interest: Dr Marra has participated in advisory boards for GlaxoSmithKline plc, and has received grants from Pfizer Inc and Abbvie Inc to conduct patient preferences research. Messrs Khakban and Zafari and Drs Sin, FitzGerald, Ng, McManus, Hollander, and Sadatsafavi have reported to CHEST that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

Role of sponsors: Funds from the Institute for Heart + Lung Health were used to support the study design and acquisition of the data. Genome Canada: Genome British Columbia, Providence, St. Paul’s Hospital Foundation, PROOF Centre, National Sanitarium Association, and the Canadian Respiratory Research Network provided staff salary and infrastructure support. None of the sponsors played any roles in the design or conduct of the study or the interpretation and dissemination of the results.

Mannino DM, Buist AS. Global burden of COPD: risk factors, prevalence, and future trends. Lancet. 2007;370(9589):765-773. [CrossRef] [PubMed]
 
Chapman KR, Bourbeau J, Rance L. The burden of COPD in Canada: results from the Confronting COPD survey. Respir Med. 2003;97(suppl C):S23-S31. [CrossRef] [PubMed]
 
Burge S, Wedzicha JA. COPD exacerbations: definitions and classifications. Eur Respir J Suppl. 2003;41:46s-53s. [CrossRef] [PubMed]
 
O’Reilly JF, Williams AE, Rice L. Health status impairment and costs associated with COPD exacerbation managed in hospital. Int J Clin Pract. 2007;61(7):1112-1120. [CrossRef] [PubMed]
 
Bastin AJ, Starling L, Ahmed R, et al. High prevalence of undiagnosed and severe chronic obstructive pulmonary disease at first hospital admission with acute exacerbation. Chron Respir Dis. 2010;7(2):91-97. [CrossRef] [PubMed]
 
Government of Canada. Population, urban and rural, by province and territory (British Columbia). Statistics Canada website. http://www.statcan.gc.ca/tables-tableaux/sum-som/l01/cst01/demo62k-eng.htm. 2011. Accessed March 12, 2015.
 
British Columbia Ministry of Health. Vital statistics births and deaths-data extract. Population Data BC website. http://www.popdata.bc.ca/data. 2014. Accessed March 1, 2015.
 
British Columbia Ministry of Health. Consolidation file (MSP registration and premium billing)-data extract. Population Data BC website. http://www.popdata.bc.ca/data. 2014. Accessed March 1, 2015.
 
British Columbia Ministry of Health. Medical Services Plan (MSP) payment information file-data extract. Population Data BC website. http://www.popdata.bc.ca/data. 2014. Accessed March 1, 2015.
 
British Columbia Ministry of Health. Discharge abstract database (hospital separations). V2. Population Data BC website. http://www.popdata.bc.ca/data. 2012. Accessed March 1, 2015.
 
British Columbia Ministry of Health. Home and community care-data extract. Population Data BC website. http://www.popdata.bc.ca/data. 2014. Accessed March 1, 2015.
 
British Columbia Ministry of Health. PharmaNet-data extract. Data Stewardship Committee. Population Data BC website. http://www.popdata.bc.ca/data. 2013. Accessed March 1, 2015.
 
Gershon AS, Wang C, Guan J, Vasilevska-Ristovska J, Cicutto L, To T. Identifying individuals with physician diagnosed COPD in health administrative databases. COPD. 2009;6(5):388-394. [CrossRef] [PubMed]
 
Bedouch P, Sadatsafavi M, Marra CA, FitzGerald JM, Lynd LD. Trends in asthma-related direct medical costs from 2002 to 2007 in British Columbia, Canada: a population based-cohort study. PLoS ONE. 2012;7(12):e50949. [CrossRef] [PubMed]
 
Poole B, Robinson S, MacKinnon M. Resource intensity weights and Canadian hospital costs: some preliminary data. Healthc Manage Forum. 1998;11(1):22-26. [CrossRef] [PubMed]
 
Canadian MIS Database (CMDB) hospital financial indicators. Canadian Institute for Health Information website. https://secure.cihi.ca/estore/productSeries.htm?pc=PCC137. Accessed January 26, 2015.
 
Government of Canada. Consumer price index, health and personal care, by province (British Columbia). Statistics Canada website. http://www.statcan.gc.ca/tables-tableaux/sum-som/l01/cst01/econ161k-eng.htm. Accessed March 10, 2015.
 
Miller JD, Foster T, Boulanger L, et al. Direct costs of COPD in the U.S.: an analysis of Medical Expenditure Panel Survey (MEPS) data. COPD. 2005;2(3):311-318. [CrossRef] [PubMed]
 
Camp PG, Chaudhry M, Platt H, et al. The sex factor: epidemiology and management of chronic obstructive pulmonary disease in British Columbia. Can Respir J. 2008;15(8):417-422. [PubMed]
 

Figures

Figure Jump LinkFigure 1 –  Number of patients with, and annual excess costs (total and by component) of, COPD, 2001 through 2010. All costs are in CAD. CAD = Canadian dollars.Grahic Jump Location
Figure Jump LinkFigure 2 –  A, B, Excess costs of COPD in different sex and age groups. All costs are in 2010 CAD. A, Excess costs in total. B, Excess costs by cost components. See Figure 1 legend for expansion of abbreviation.Grahic Jump Location
Figure Jump LinkFigure 3 –  A, B, Monthly excess costs of COPD from index date. All costs are in 2010 CAD. A, Excess costs in total. The first month is excluded from this graph because of its very high total cost value ($5,424). B, Excess costs by relative contribution of cost components. See Figure 1 legend for expansion of abbreviation.Grahic Jump Location
Figure Jump LinkFigure 4 –  Monthly excess costs of COPD according to the initial diagnosis condition. All costs are in 2010 CAD. The first month is excluded from this graph because of its very high value of inpatient-first cost ($12,372). See Figure 1 legend for expansion of abbreviation.Grahic Jump Location

Tables

Table Graphic Jump Location
TABLE 1 ]  Baseline Characteristics of the COPD and Comparison Cohorts

References

Mannino DM, Buist AS. Global burden of COPD: risk factors, prevalence, and future trends. Lancet. 2007;370(9589):765-773. [CrossRef] [PubMed]
 
Chapman KR, Bourbeau J, Rance L. The burden of COPD in Canada: results from the Confronting COPD survey. Respir Med. 2003;97(suppl C):S23-S31. [CrossRef] [PubMed]
 
Burge S, Wedzicha JA. COPD exacerbations: definitions and classifications. Eur Respir J Suppl. 2003;41:46s-53s. [CrossRef] [PubMed]
 
O’Reilly JF, Williams AE, Rice L. Health status impairment and costs associated with COPD exacerbation managed in hospital. Int J Clin Pract. 2007;61(7):1112-1120. [CrossRef] [PubMed]
 
Bastin AJ, Starling L, Ahmed R, et al. High prevalence of undiagnosed and severe chronic obstructive pulmonary disease at first hospital admission with acute exacerbation. Chron Respir Dis. 2010;7(2):91-97. [CrossRef] [PubMed]
 
Government of Canada. Population, urban and rural, by province and territory (British Columbia). Statistics Canada website. http://www.statcan.gc.ca/tables-tableaux/sum-som/l01/cst01/demo62k-eng.htm. 2011. Accessed March 12, 2015.
 
British Columbia Ministry of Health. Vital statistics births and deaths-data extract. Population Data BC website. http://www.popdata.bc.ca/data. 2014. Accessed March 1, 2015.
 
British Columbia Ministry of Health. Consolidation file (MSP registration and premium billing)-data extract. Population Data BC website. http://www.popdata.bc.ca/data. 2014. Accessed March 1, 2015.
 
British Columbia Ministry of Health. Medical Services Plan (MSP) payment information file-data extract. Population Data BC website. http://www.popdata.bc.ca/data. 2014. Accessed March 1, 2015.
 
British Columbia Ministry of Health. Discharge abstract database (hospital separations). V2. Population Data BC website. http://www.popdata.bc.ca/data. 2012. Accessed March 1, 2015.
 
British Columbia Ministry of Health. Home and community care-data extract. Population Data BC website. http://www.popdata.bc.ca/data. 2014. Accessed March 1, 2015.
 
British Columbia Ministry of Health. PharmaNet-data extract. Data Stewardship Committee. Population Data BC website. http://www.popdata.bc.ca/data. 2013. Accessed March 1, 2015.
 
Gershon AS, Wang C, Guan J, Vasilevska-Ristovska J, Cicutto L, To T. Identifying individuals with physician diagnosed COPD in health administrative databases. COPD. 2009;6(5):388-394. [CrossRef] [PubMed]
 
Bedouch P, Sadatsafavi M, Marra CA, FitzGerald JM, Lynd LD. Trends in asthma-related direct medical costs from 2002 to 2007 in British Columbia, Canada: a population based-cohort study. PLoS ONE. 2012;7(12):e50949. [CrossRef] [PubMed]
 
Poole B, Robinson S, MacKinnon M. Resource intensity weights and Canadian hospital costs: some preliminary data. Healthc Manage Forum. 1998;11(1):22-26. [CrossRef] [PubMed]
 
Canadian MIS Database (CMDB) hospital financial indicators. Canadian Institute for Health Information website. https://secure.cihi.ca/estore/productSeries.htm?pc=PCC137. Accessed January 26, 2015.
 
Government of Canada. Consumer price index, health and personal care, by province (British Columbia). Statistics Canada website. http://www.statcan.gc.ca/tables-tableaux/sum-som/l01/cst01/econ161k-eng.htm. Accessed March 10, 2015.
 
Miller JD, Foster T, Boulanger L, et al. Direct costs of COPD in the U.S.: an analysis of Medical Expenditure Panel Survey (MEPS) data. COPD. 2005;2(3):311-318. [CrossRef] [PubMed]
 
Camp PG, Chaudhry M, Platt H, et al. The sex factor: epidemiology and management of chronic obstructive pulmonary disease in British Columbia. Can Respir J. 2008;15(8):417-422. [PubMed]
 
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