Estimating the Under-reporting Rate for Infectious Gastrointestinal Illness in Ontario

Abstract

Background: In Ontario, infectious gastrointestinal illness (IGI) reporting can be represented by a linear model of several sequential steps required for a case to be captured in the provincial reportable disease surveillance system. Since reportable enteric data are known to represent only a small fraction of the total IGI in the community, the objective of this study was to estimate the under-reporting rate for IGI in Ontario.Methods: A distribution of plausible values for the under-reporting rate was estimated by specifying input distributions for the proportions reported at each step in the reporting chain, and multiplying these distributions together using simulation methods. Input distributions (type of distribution and parameters) for the proportion of cases reported at each step of the reporting chain were determined using data from the Public Health Agency of Canada's National Studies on Acute Gastrointestinal Illness (NSAGI) initiative. Results:For each case of enteric illness reported to the province of Ontario, the estimated number of cases of IGI in the community ranged from 105 to 1,389, with a median of 285, and a mean and standard deviation of 313 and 128, respectively.Conclusions: Each case of enteric illness reported to the province of Ontario represents an estimated several hundred cases of IGI in the community. Thus, reportable disease data should be used with caution when estimating the burden of such illness. Program planners and public health personnel may want to consider this fact when developing populationbased interventions.MeSH terms: Gastroenteritis; infectious disease reporting; surveillance; Ontario; Canada La traduction du résumé se trouve à la fin de l'article.

Published Case Studies of Waterborne Disease Outbreaks—Evidence of a Recurrent Threat

“…Relying on evidence from laboratory testing of stool specimens is limited by several factors, as follows ( Moe, 2001 ): an infection may not produce symptoms, an infected person may not seek medical attention, the healthcare provider may not take a stool specimen or the patient may not provide one, the appropriate laboratory test may not be requested, the test may be done incorrectly or may be unable to detect pathogens present, and the laboratory may not report the result in a timely manner or at all. A study of underreporting of gastrointestinal disease in Ontario, Canada ( Majowicz et al, 2005 ), estimated that, for each case reported to the province, there was an estimated median of 285 cases in the community (range 195 to 555). In this analysis, 67 cases were estimated to visit a physician, 17 had a stool sample requested, 14 were submitted, 13 were analyzed, and only 1.5 tested positive.…”

Estimating the Burden of Acute Gastroenteritis, Foodborne Disease, and Pathogens Commonly Transmitted by Food: An International Review

“…When national estimates are determined, they must take into account the burden of illness that is not ascertained by routine surveillance. Because many patients with acute gastroenteritis do not visit a health care provider or do not submit a specimen for laboratory testing [5,6,23,24], clinical and laboratoryconfirmed diagnoses greatly underestimate the burden of illness in the community. When the burden of acute gastroenteritis is known, food-specific and pathogen-specific estimates can be calculated.…”

“…The public health reporting study focused on reporting practices at the health-unit level. Based on these studies, it was calculated that each case of acute gastroenteritis reported to the Provincial Health Authority represented between 105 and 1389 community cases, with a mean of 313 cases [23].…”

Epidemiology of Enteric Disease in C‐EnterNet’s Pilot Site – Waterloo Region, Ontario, 1990 to 2004

“…Under-reporting is a problem in reportable disease data (1)(2)(3)(8)(9)(10)(11)(12)(13)(14)(15)(16), and the rates calculated for the present study are based on reported cases. Recent work (8) at the national level estimated the number of community cases of salmonellosis, campylobacteriosis and VTEC infection that can be expected per case reported nationally.…”