National Studies on Acute Gastrointestinal Illness (NSAGI)

Background

Health Canada's NSAGI (National Studies on Acute Gastrointestinal Illness) initiative consists of a number of interrelated and complimentary studies that together will provide the first population level incidence data of AGI in Canada. In addition, it will describe and quantify under-reporting at each stage of Canada's national surveillance systems and estimate the burden associated with AGI.

NSAGI was initiated in response to a food safety and nutrition cabinet memorandum. Additionally, the Laboratory Centre for Disease Control (LCDC) Food and Water Safety Program Plan 2000-2003 (Draft, June 23, 2000) identified population based surveillance and baseline studies as key areas for enhancement. Program enhancements recommended in this document include:

• Enhancement and broadening of the Acute Enteric Surveillance Program to provide population based surveillance capacity for enteric pathogens including antimicrobial resistant pathogens.
• Development of databases and expertise in the analysis of co-factors which may affect trends in food and waterborne disease (Canada's Food Net).
• Carry out national base-line studies of the numbers, risk factors and socio-economic burden of enteric, food and waterborne diseases.

NSAGI has been formally endorsed by the Enteric Disease Surveillance (ENDS) Steering Committee, an external advisory committee for Centre for Infectious Disease Prevention and control (CIDPC).

Why are these studies needed?

Accurate estimates of disease prevalence and burden are central to the development of sound public health policy. Disease surveillance plays a fundamental role in informing these estimates. Although Canada has well-established surveillance for enteric disease, limitations are inherent in this passive surveillance data. Consequently, there are significant gaps in information describing the magnitude of enteric disease at the population level. To be included in the surveillance system, an individual must first present to a medical care provider and submit a specimen for microbiological testing. Data on selected laboratory-confirmed cases are then transferred through the illustrated reporting pyramid. This process captures only a fraction of enteric disease episodes occurring in the community. Although under-reporting is well recognised by the public health community, the lack of any quantification frustrates attempts to make accurate population level estimates from existing surveillance data.

Improved estimates of the prevalence and burden of enteric diseases at a population level will aid in the development of sound public health policy and assist in:

• prioritizing public health needs;
• guiding the development of prevention, management and/or treatment programs;
• mobilizing resources to address problems;
• providing focus for targeted epidemiological studies.

How will NSAGI help?

Through a series of population based studies, NSAGI will provide data describing the prevalence of acute gastrointestinal illness in multiple sites across Canada.

NSAGI will provide the necessary information to quantify and describe under-reporting at each 'step' in the reporting pyramid. Multiplication factors can then be calculated and applied to existing surveillance data to correct for under-reporting and thus more accurately reflect disease prevalence in the population.

NSAGI will also provide a framework to further develop studies focusing on risk factors, chronic sequelae and economic costs of enteric diseases. This information will guide the development of prevention programs, including educational materials for the public.

Who's involved?

Provincial and Local Public Health Professionals have partnered with Health Canada to develop these studies. The national based studies (laboratory and public health reporting) have been developed in conjunction with provincial laboratory directors and epidemiologists. The regional based studies (population and physician) have been developed in conjunction with provincial epidemiologist and other local other local health professionals.

NSAGI Components

The four components of the overall NSAGI framework are as follows (approximate time frames shown in brackets):

1. Prevalence and Under-reporting (2000 - 2003)
   A series of studies will estimate the period prevalence of AGI at the community level and quantify the under-reporting of enteric diseases at various stages in Canada's passive surveillance system. The burden associated with AGI will also be estimated.

2. Community Aetiology (2002 - 2004)
   As a follow-on from component one, the community etiology will focus on understanding the infectious causes of AGI in the community and pathogen specific under-reporting rates.

3. Chronic Sequelae (2003 - 2005)
   Long term sequelae associated with enteric pathogens contribute to the overall burden associated with AGI. This study will estimate the significance of chronic sequelae in Canada.

4. Risk Factors (on-going)
   To develop effective and appropriate interventions, factors associated with an increased risk of disease need to be identified. These case control studies will focus on pathogens and populations of importance.

Component One: prevalence and under-reporting

The interrelated studies forming the basis of NSAGI's first component (incidence and under-reporting) will form a solid foundation upon which further targeted studies, focussing on aetiology, chronic sequelae and risk factors, will be developed.

The findings of these studies will be of value to local and public health officials across the country, the Canadian Food Inspection Agency, the Bureau of Microbiology and Bureau of Infectious Diseases in Health Canada, The Enteric Disease Surveillance Steering Committee and public and private microbiology laboratories.

Project Objectives:

The objectives of the incidence and under-reporting studies (component one) are as follows:

• To determine the magnitude and distribution of self reported AGI in the community;
• To estimate the burden associated with AGI;
• To describe and quantify the magnitude of under-reporting of AGI at each stage along the national enteric disease surveillance systems; and
• To identify modifiable factors affecting under-reporting that if altered, could reduce case loss throughout the surveillance system.

Project Scope:

To accomplish the project objectives mentioned above, the following four studies will be conducted as part of component one:

1. Population Study
   The population survey, administered by telephone, is designed to determine the period prevalence and burden of illness of AGI in selected sites. The study has commenced in the city of Hamilton (n = 3500, sampled over a 12 month period) and will be expanded to include additional sites across Canada. A working group will identify appropriate sites. Efforts will be made to secure the inclusion of rural and First Nation communities as future sites. A steering committee will be assembled to oversee the expansion of this study.

2. Physician Study
   The physician survey will focus on the under-reporting of AGI at the patient-physician interface. Of the patients consulting a physician, the percentage diagnosed with AGI will be determined. Physicians will be questioned about when and why stool specimens are requested, patient compliance to stool submission requests and the reporting of results if an etiologic agent is identified. This paper-based survey will be administered to all family and paediatric physicians in each of the sites selected for the population study, beginning with the Hamilton site.

3. Laboratory Study
   The laboratory study will describe and quantify the under-reporting of AGI at the phase when a stool sample is analysed for enteric pathogens. A self-administered paper based survey of all the microbiological laboratories that process stool specimens in Canada (n = 535) will be conducted. Key variables influencing the probability of a pathogen being identified in a stool specimen and laboratory reporting practices will be identified and described.

4. Public Health Reporting Study
   The public health reporting study will focus on under-reporting from the local Health Unit to the National level. The flow of information will be described and the loss of cases as they move up the surveillance chain will be quantified.

This project will provide a sound reference point for policy makers and researchers who require accurate baseline data. Multiplication factors will be derived to account and correct for under-reporting along the national enteric surveillance chain allowing existing surveillance data to be interpreted with more accuracy and confidence.

This project is national in its approach. Multiple sites will be selected across the country with an aim of making the composite sample broadly reflective of the national population.

For further detail, please contact us.