Systematic review of foodborne burden of disease studies: quality assessment of data and methodology.

Burden of disease (BoD) studies aim to identify the public health impact of different health problems and risk factors. To assess BoD, detailed knowledge is needed on epidemiology, disability and mortality in the population under study. This is particularly challenging for foodborne disease, because of the multitude of causative agents and their health effects. The purpose of this study is to systematically review the methodology of foodborne BoD studies. Three key questions were addressed: 1) which data sources and approaches were used to assess mortality, morbidity and disability?, 2) which methodological choices were made to calculate Disability Adjusted Life Years (DALY), and 3) were uncertainty analyses performed and if so, how? Studies (1990-June 2012) in international peer-reviewed journals and grey literature were identified with main inclusion criteria being that the study assessed disability adjusted life years related to foodborne disease. Twenty-four studies met our inclusion criteria. To assess incidence or prevalence of foodborne disease in the population, four approaches could be distinguished, each using a different data source as a starting point, namely 1) laboratory-confirmed cases, 2) cohort or cross-sectional data, 3) syndrome surveillance data and 4) exposure data. Considerable variation existed in BoD methodology (e.g. disability weights, discounting, age-weighting). Almost all studies analyzed the effect of uncertainty as a result of possible imprecision in the parameter values. Awareness of epidemiological and methodological rigor between foodborne BoD studies using the DALY approach is a critical priority for advancing burden of disease studies. Harmonization of methodology that is used and of modeling techniques and high quality data can enlarge the detection of real variation in DALY outcomes between pathogens, between populations or over time. This harmonization can be achieved by identifying substantial data gaps and uncertainty and establish which sequelae of foodborne disease agents should be included in BoD calculations.