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Table 3 Characteristics of clinical burden studies included in the review

From: Clinical, economic, and humanistic burden of asthma in Canada: a systematic review

Reference/Study period

Data source

Study objective

Inclusion criteria

Asthma definition

Retrospective cohort studies

Sadatsafavi et al. 2010 [10] 1996 - 2000

Administrative healthcare data

Determine direct medical costs of asthma-related healthcare in British Columbia

5 to 55 years

Narrow: ICD-9 493.x Broad: visits for an asthma-related diagnosis; hospitalizations with asthma among the discharge diagnoses

≥4 asthma prescriptions in 1 year

≥1 asthma hospitalization

≥2 physician visits for asthma

Blais et al. 2011 [18] 1998 - 2005

RAMQ database,

Determine relationship between better use of LTRA and asthma exacerbations in children

5-15 years

Moderate or severe asthma exacerbations - an ED visit for asthma, a hospital admission for asthma, or a dispensed short-course (14 days) prescription of oral corticosteroids

Diagnosed asthma

Initiating (mono)therapy with ICS or LTRA

Rosychuk et al. 2010 [19] Apr 1999 to Mar 2005

Provincial administrative healthcare databases

Describe the epidemiology of asthma presentations to EDs for 3 main regions in the province of Alberta

All people registered under the AHCIP at any time in a given year

ICD-9 code 493.x or ICD-10 code J45.x as the first or second diagnosis fields in the ACCS

Crighton et al. 2001 [20] Apr 1, 1988 to Mar 31, 2000

DAD database at CIHI,

Examine the seasonal patterns and trends of asthma hospitalizations in relation to age and gender

NR

ICD-9-CM code 493

Ungar et al. 2011 [21] Nov 1, 2000 to Mar 31, 2003

Interview data linked to administrative healthcare data.

Identify factors associated with asthma exacerbation causing ED visits or hospitalizations related to health status, socioeconomic status (SES), and drug insurance

1 to 18 years

Physician-diagnosed asthma; ICD-9 493 or ICD-10 J45

Disano et al. 2010 [22] 2003 - 2006

DAD database from CIHI, INSQP Deprivation Index, Statistics Canada Community Profiles

Examine inequalities between SES groups with respect to rates of ACSC-hospitalizations

Acute care cases of 0 to 75 years; asthma in children for age <20 years

NR

Blais et al. 2009 [18] 2002 - 2004

RAMQ database

Compare the use of healthcare services between new users of budesonide/formoterol and F/S

Asthma patients aged 16 to 65 years ≥1 claim for combination therapy in 2002 or 2003 and no claims for combination therapy for ≥1 year prior to first claim

ICD-9 codes 493.0, 493.1, 493.9

Rowe et al. 2009 [23] 1 Apr 1999–31 Mar 2005

ACCS and other provincial databases.

Describe the epidemiology of asthma presentations to EDs made by adults in the province of Alberta, Canada

Asthmatic individuals aged 18 years

ICD-9 493.x or ICD-10 J45.x

To et al. 2008 [24] 1994 - 1998

DAD database from CIHI, OHIP records, RPDB database

Describe the prevalence of asthma; all-cause mortality; physician visits and hospitalizations for asthma and all causes; and seasonal and geographical variation of healthcare utilization in children

Children aged 0 to 9 years

At least 1 asthma hospitalization or 2 asthma OHIP claims within 3 years

Lemiere et al. 2007 [25] 2001 - 2004

RAMQ database, WRA patients

Compare clinical characteristics and use of medical resources between subjects with OA, WEA, and WRA

NR

Physician-diagnosed asthma OA, WEA, and WRA

To et al. 2007 [26] 1994 to 2006

HMDB database from CIHI, OHIP records, RPDB database;

Examine and predict the persistence of childhood asthma

Children born in 1994 diagnosed with asthma before their 6th birthday, followed up until their 12th birthday

1 asthma hospitalization or 2 asthma physician claims within 3 years prior to age 6 years (ICD-9 493 or ICD-10 J45). Persistent asthma - additional claims during follow-up Remission asthma - no additional claims

Agha et al. 2007 [27] 1993 - 2001

DAD database at CIHI, SES from the 1996 Census data

Examine socioeconomic disparities in ACS and non-ACS admissions among birth cohorts in a universal health insurance setting

Children born alive in Toronto during 1993–2001

The most responsible diagnosis in the CIHI DAD DB

Gershon et al. 2007 [2] 1994/95 to 2001/202

DAD from CIHI, OHIP

Understand the burden of asthma

Asthma patients from ON, aged 0–39 years

1 DAD hospitalization record or 2 OHIP claims for asthma in a 3-year period

Lougheed et al. 2006 [28] 2001 - 2002

CIHI

Assess regional differences in ED visit rates and hospitalizations for asthma

ED visits for asthma

ICD-10 code J45.x

Dik et al. 2006 [29] 1985 - 1998

Manitoba administrative healthcare data

Study 14-year trends in utilization of physician resources for asthma and compare them to trends for allergic rhinitis

NR

ICD-9-CM code 493

Sin et al. 2001 [30] FY 1992 - 1996

CIHI, drug claims, physician billing, and mortality databases

Determine the impact of ICS on rehospitalization for asthma and all-cause mortality rates in elderly patients

Asthmatic patients, aged ≥65 years, who had been hospitalized with a most responsible diagnosis of asthma in the past 5 years

ICD-9 codes 493.0, 493.1, and 493.9

Prospective cohort studies

Rowe et al. 2010 [31] 2004 – 2005

Interviews

Describe factors associated with admission to hospital for acute asthma after ED treatment

Patients aged 18 to 55 years diagnosed with asthma

Patient-reported

Sin et al. 2003 [32] 1985, 1988

AHCIP data,

Determine the relationship between SES and ED visits for asthma in a free access healthcare system.

Children born 1985 to 1988 followed for 10 years

ICD-9 code 493.x

Ungar et al. 2001 [33] May - Oct 1995

Telephone interviews at 1, 3, and 6 months,

Assess the cost of asthma care at the patient level in children from the perspectives of society, the Ontario Ministry of Health, and the patient.

Patients or caregivers filling prescriptions for bronchial inhalers

Probable asthma - a prescription for a bronchial inhaler medication in the last month (bronchodilator or corticosteroid) and reported experiencing shortness of breath, wheeze, or recurrent cough in the past

Anis et al. 2000 [34] Sept 1, 1994 - Aug 31 1995

Hospital ED, telephone interview for follow-up

Estimate the average direct cost of illness for 4 cardiorespiratory conditions

ED visitors who completed follow-up interviews

ED visit records

Rowe et al. 2007 [23] 1996-1998

Structured ED interview and telephone follow-up 2 weeks later

Compare ED asthma management and outcomesbetween Canada and US

Patients aged 2 to 54 years who presented with acute asthma in ED

NR

Cross-sectional studies

Boulet et al. 2008 [35] April - August 2004,

Telephone survey

Assess the influence of current and former smoking on self-reported asthma control and healthcare use

Adults aged 18 to 54 years with physician-diagnosed asthma for ≥6 months

Patient-reported or physician-diagnosed asthma

Klomp et al. 2008 [36] 2002/03 and 2003/04

Health databases in Saskatchewan

Describe the quality of asthma care using a set of proposed quality indicators

Saskatchewan residents who had a valid health insurance number

Over 1-year period: ≥3 prescriptions for antiasthma drug or ≥2 physician claims (ICD-9 code 493) or ≥2 hospitalization claims (ICD-9 493.x or ICD-10 J45.x) or ≥1 claim for physician services or hospitalization for asthma plus ≥1 pharmacy claim for an antiasthma drug

Iron et al. 2003 [37] 1994/1995

CNPHS data, OHIP

Determine the association between demographics, access to care, SES, and need (comorbidities) with actual family physician costs

Survey respondents aged ≥25 years consenting to share HC# and responses with MOHLTC

Self-reported

Anis et al. 2001 [38] 1995

Ministry of Health administrative databases

Determine whether excessive use of SABA, in conjunction with underuse of ICS, would be a marker for poorly controlled asthma and excessive use of healthcare resources

Asthma patients aged 5 to 50 years for whom ≥1 prescription for a SABA was filled in 1995

Patients filling SABA prescriptions; for hospitalizations, ICD-9 code 08 (diseases of the respiratory system)

Baibergenova et al. 2005 [39] April 1, 2001 to March 31, 2004

 

Examine the pattern and strength of seasonal fluctuations in ED visits due to asthma

Asthma patients with ED visits for asthma or status asthmaticus

ICD-9 code 493.x or ICD-10 J45.0–J45.9

Lynd et al. 2004 [40] NR

Survey

Assess the association between SES and SABA use, controlling for asthma severity

Asthmatic patients aged 19 to 50 years residing in the Greater Vancouver Regional District of British Columbia

NR

Case–control study

Suissa et al. 2002 [41] 1975 - 1997

Saskatchewan Health DB

Assess whether regular use of ICS prevents asthma hospitalizations

Source cohort: subjects aged 5–44 years receiving ≥3 prescriptions of an antiasthma medication in any 1-year period Full cohort: all subjects with ≥1 year follow-up, irrespective of whether they were admitted to hospital for asthma during the baseline year

Primary discharge diagnosis of asthma (ICD-9 codes 493.0, 493.1, or 493.9)

Health economic analysis

Seung et al. 2005 [42] 2004

NACRS at CIHI, OCCI, MOHLTC billing

Determine the use of urgent care resources and annual costs for the uncontrolled asthmatic population in Canada

NR

ICD-9 Code 493

  1. ACCS=ambulatory care classification system, ACSC=ambulatory care-sensitive conditions, AHCIP=Alberta Healthcare Insurance Plan, CIHI=Canadian Institute for Health Information, CNPHS=Canadian National Population Health Survey, DAD=Discharge Abstract Database, ED=emergency department, HMDB=Hospital Morbidity Database, ICS=inhaled corticosteroid, ICD=International Classification of Diseases, LTRA=leukotriene receptor antagonist, MOHLTC=Ministry of Health and Long Term Care, NACRS=National Ambulatory Care System, NR=not reported, OA= occupational asthma, OCCI=Ontario Case Costing Initiative, OHIP=Ontario Health Insurance Plan, RAMQ=Régie de l’assurance maladie du Québec, RPDB=Registered Persons Database, SES=socioeconomic status, WEA=work-exacerbated asthma, WRA=work-related asthma.