Estimating Salmonella and Campylobacter Underreporting

An extensive literature review was conducted to identify studies (of designs presented above) that estimate ascertainment or reporting rates for salmonellosis and campylobacteriosis in European Union Member States (MS), plus European Free Trade Area (EFTA) countries Iceland, Norway and Switzerland and all other OECD countries. Articles were considered relevant if they: measured the sensitivity of reporting or reported the rate of UA, UR or UE; reported MFs, measured a new incidence or prevalence of infection from which a MF could be derived; or used any alternative methodology to correct surveillance or notification data. To identify appropriate studies, a literature review for each disease (salmonellosis and campylobacteriosis) and each pathogen (Salmonella spp. and Campylobacter spp.) was conducted in PubMed using the search terms: burden, cost-of-illness, cost of disease, cost-effectiv*, cost-analys*, cost-benefit, cost-utility, disability-adjusted, mathematical model*, multiplication factor*, multiplier*, outbreak*, prospective stud*, quality of life, quality-adjusted, serological stud*, serological survey*, serosurveillance, sero-surveillance, seroprevalence, statistical model*, telephone (*denotes any ending to the search term); linked by 'OR’. The search was restricted to articles written in English and to the years 1990–2011 since surveillance systems, reporting protocols and epidemiological patterns may have been different in the years preceding 1990, hence MFs would be less appropriate for adjusting current surveillance and notification data.
Following identification of these studies, MFs were either taken directly from the literature or derived where the proportion of underestimated, under-ascertained, or underreported cases was known (MF = 100/(percentage reported or ascertained or estimated), Figure 
1B). MFs for salmonellosis and campylobacteriosis were compared to gain an understanding of variation between and within countries when using different methods to estimate UR and UA.