Indirect Cost of Illness Study of Moderate and Severe Asthma in Quebec

Rationale Asthma is a chronic inflammatory disorder of the airways affecting persons of all ages and is recognized as one of the most common chronic diseases. With a continuously increasing prevalence and associated morbidity and mortality, asthma poses a tremendous clinical and economic burden on healthcare systems and on the society as a whole.

According to a report published by the Global Initiative for Asthma (GINA) in 2004 an estimated 300 million people in the world have asthma, and more than 2 million Canadians have asthma. Canada has one of the highest asthma prevalence rates in the world (8.5%, aged 12 and over) and it is a major cause of hospitalization.

The direct and indirect costs associated with asthma are expected to rank among the highest for chronic diseases due to the high prevalence in conjunction with the significant healthcare utilization associated with the disease and the considerable restrictions asthma imposes on the physical, emotional, social, and professional lives of sufferers. The cost of asthma varies dramatically across disease severity, and it is expected that these costs are greater when the condition is sub-optimally managed and controlled. Although a number of publications have been reported on the economic burden of asthma, there is a lack of information on the cost of asthma based on disease severity and level of disease control in Canada. Moreover, no study has compared the annual cost of uncontrolled and "well-controlled" asthma patients. Although population-level direct costs have been previously reported through the use of administrative healthcare databases in various provinces, these databases cannot provide clinical data and are limited to subjects who have a public drug insurance plan.

The proposed study aims to i) estimate the annual indirect cost of asthma and ii) the impact of asthma on absenteeism, presenteeism and work productivity in Canada. This information is essential to further quantify the burden of asthma on patients and the healthcare system in the Canadian setting.

Overall Objectives The overall objective of this study is to describe the impact of asthma on patients with moderate to severe asthma and to estimate the indirect costs of asthma care in asthmatic patients followed in tertiary clinics specialized in the field of asthma in Quebec, Canada.

Primary objectives

• To estimate the annual indirect costs of asthma in asthmatic patients followed in tertiary clinics specialized in the field of asthma in Quebec, Canada
• To estimate the annual indirect cost of asthma by asthma severity and control status (uncontrolled, partly controlled, well controlled) of asthmatic patients followed in tertiary clinics specialized in the field of asthma in Quebec, Canada

Secondary objectives

• To determine the impact of asthma on work productivity in asthmatic patients followed in tertiary clinics specialized in the field of asthma in Quebec, Canada.

Study Design

A prospective cohort study will be conducted to measure the indirect economical burden of asthma on patients. Patients will be selected and recruited from the BD-Asthma registry and followed prospectively for 1 year. Recruited patients will be asked to complete questionnaires at regular intervals for 1 year to measure indirect cost of disease, using the Valuation of lost productivity (VOLP) questionnaire.

Recruitment of patients All eligible patients from the BD-asthma will be invited to participate. Patients approached for participation will be provided verbal and written information on the project and, if the patient agrees to participate, they will be asked to sign the participation consent form. The forms will be collected by the research coordination centre (either at the clinic or the physicians' office or directly with the patient). All recruited eligible patients that have provided their consent will be included in this study.

Source Population The population is defined as individuals diagnosed with asthma (ICD9 codes 493.x).

Study Population The study population is defined as having had at least one diagnosis of asthma (ICD9 codes 493.x) recorded in the BD Asthma database between February 2010 and February 2012.

Clinical information Patient characteristics and clinical information on asthma will be obtained from the BD-asthma database.

Data Collected For each patient, the following data will be collected

• Patient demographics
• Age
• Sex
• Income
• Level of education
• Smoking
• Disease management and Treatment utilization in the year prior to recruitment
• Physician visits and follow up
• Hospitalizations (number and total days)
• Emergency room visits
• Disease characteristics
• Asthma history
• Year of first diagnosis of asthma severity
• Asthma Control Questionnaire score
• Lung function measures

Data Analysis Methods For each participant, the percentage of time missed from work over a year will be calculated. We will use the human capital approach to calculate the costs of asthma due to lost productivity, incorporating both absenteeism and presenteeism in the calculation of the productivity loss. We will calculate the number of work days in which the person was unable to attend the workplace, and the number of days and percentage of time lost during the days the person's work was affected by their asthma. The fraction of time lost from work in the past year will be multiplied by the average income in Quebec. Finally, this value will be multiplied by the coefficient generated by the VOLP, which reflects the relative value of the productivity loss. In addition, we will calculate the VOLP multiplier for each participant which, combined with the percentage of time missed from work, will create a measure of productivity loss adjusted for the relative importance and replace-ability of the participant's profession.

Sample Size and Power

One hundred subjects will be randomly selected from the BD-Asthma registry.

Limitations

The study population may not be representative of the general asthma population, as moderate to severe asthma will be over represented in these tertiary centers.

Inclusion criteria

• Part of the BD-Asthma registry
• Age 18 years and older
• Patients who signed consent for research with the BD-Asthma registry and signed consent to participate in the indirect cost study.
• Must be alive at the time of recruitment

Exclusion criteria

• Patients with a diagnosis of COPD recorded in BD-Asthma at the time of enrolment.