A systematic review of the methodological considerations in Campylobacter burden of disease studies

Background: Campylobacteriosis is a major zoonotic and foodborne disease (FBD), posing a substantial social and health economic burden on human health. Burden of disease (BoD) studies, which increasingly use the disability-adjusted life years (DALYs) metric, provide comprehensive insights into disease effects. However, the complexity of DALY calculations, combined with diverse causative agents and research gaps, complicates cross-regional comparisons. This review evaluates existing Campylobacter BoD studies and interrogates their methodological approaches and assumptions in quantifying DALYs.

Methods/Principal findings: A systematic search of PubMed, EMBASE, Web of Science, and selected grey literature databases was conducted to identify existing Campylobacter BoD studies. Studies assessing the BoD methodology and calculation using the DALY framework were considered. In total, 23 studies met the predefined inclusion criteria. Of these, 19 were single-country studies, while 4 were multi-country analyses. A significant data gap exists, with limited or no studies from low- and middle-income countries (LMICs), exemplified by just one study obtained from Rwanda. Most studies used an incidence- and pathogen-based approach to estimate DALYs, excluding social weighting, in line with the Global Burden of Disease (GBD) study. Methodological discrepancies were noted, especially in disability weight (DW) assignment, health state classification, and life expectancy table usage. Most single-country studies (n=8) used national life tables rather than universal ones, challenging cross-country comparisons due to a lack of standardisation.

Conclusion: Significant variations in the methodological approaches and assumptions for Campylobacter BoD studies exist. Addressing these disparities is essential for harmonising methodological design choices using the DALYs metric to inform evidence-based public health policies and interventions.

PROSPERO registration number: The protocol for this study was registered with the International Prospective Register of Systematic Reviews (PROSPERO), which can be accessed under the registration number CRD42023414973.