title: Relationship between socioeconomic status and gastrointestinal infections in developed countries: a systematic review protocol.
abstract: BACKGROUND
  The association between low socioeconomic status (SES) and poor health is well documented in the existing literature. Nonetheless, evidence on the relationship between SES and gastrointestinal (GI) infections is limited, and the mechanisms underlying this relationship are not well understood with published studies pointing to conflicting results. This review aims to identify studies that investigate the relationship between SES and GI infections in developed countries, in order to assess the direction of the association and explore possible explanations for any differences in the risk, incidence or prevalence of GI infections across socioeconomic groups.
  
  
  METHODS
  Three systematic methods will be used to identify relevant literature: electronic database, reference list and grey literature searching. The databases MEDLINE, Scopus and Web of Science Core Collection will be searched using a broad range of search terms. Screening of the results will be performed by two reviewers using pre-defined inclusion and exclusion criteria. The reference lists of included studies will be searched, and Google will be used to identify grey literature. Observational studies reporting quantitative results on the prevalence or incidence of any symptomatic GI infections by SES, in a representative population sample from a member country of the Organisation for Economic Co-operation and Development (OECD), will be included. Data will be extracted using a standardised form. Study quality will be assessed using the Liverpool University Quality Assessment Tools (LQAT). A narrative synthesis will be performed including tabulation of studies for comparison.
  
  
  CONCLUSIONS
  This systematic review will consolidate the existing knowledge on the relationship between SES and GI infections. The results will help to identify gaps in the literature and will therefore provide an evidence base for future empirical studies to deepen the understanding of the relationship, including effective study design and appropriate data analysis methods. Ultimately, gaining insight into this relationship will help to inform policies to reduce any health inequalities identified.
  
  
  BACKGROUND
  PROSPERO CRD42015027231.
authors.affiliation: NIHR Health Protection Research Unit in Gastrointestinal Infections, University of Liverpool, Liverpool, L69 7BE, UK. Tanith.Rose@liverpool.ac.uk.|Department of Public Health and Policy, University of Liverpool, Liverpool, UK. Tanith.Rose@liverpool.ac.uk.|Department of Public Health and Policy, Institute of Psychology, Health and Society, University of Liverpool, Whelan Building, Liverpool, L69 3GB, UK. Tanith.Rose@liverpool.ac.uk.
authors.forename: Tanith C
authors.initials: TC
authors.lastname: Rose
authors.affiliation: NIHR Health Protection Research Unit in Gastrointestinal Infections, University of Liverpool, Liverpool, L69 7BE, UK. Natalie.Adams@phe.gov.uk.|Department of Public Health and Policy, University of Liverpool, Liverpool, UK. Natalie.Adams@phe.gov.uk.|Public Health England, London, UK. Natalie.Adams@phe.gov.uk.
authors.forename: Natalie
authors.initials: N
authors.lastname: Adams
authors.affiliation: NIHR Health Protection Research Unit in Gastrointestinal Infections, University of Liverpool, Liverpool, L69 7BE, UK. David.Taylor-Robinson@liverpool.ac.uk.|Department of Public Health and Policy, University of Liverpool, Liverpool, UK. David.Taylor-Robinson@liverpool.ac.uk.
authors.forename: David C
authors.initials: DC
authors.lastname: Taylor-Robinson
authors.affiliation: NIHR Health Protection Research Unit in Gastrointestinal Infections, University of Liverpool, Liverpool, L69 7BE, UK. B.Barr@liverpool.ac.uk.|Department of Public Health and Policy, University of Liverpool, Liverpool, UK. B.Barr@liverpool.ac.uk.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Barr
authors.affiliation: NIHR Health Protection Research Unit in Gastrointestinal Infections, University of Liverpool, Liverpool, L69 7BE, UK. Jeremy.Hawker@phe.gov.uk.|Public Health England, London, UK. Jeremy.Hawker@phe.gov.uk.
authors.forename: Jeremy
authors.initials: J
authors.lastname: Hawker
authors.affiliation: NIHR Health Protection Research Unit in Gastrointestinal Infections, University of Liverpool, Liverpool, L69 7BE, UK. S.J.Obrien@liverpool.ac.uk.|Institute of Infection and Global Health, University of Liverpool, Liverpool, UK. S.J.Obrien@liverpool.ac.uk.
authors.forename: Sarah
authors.initials: S
authors.lastname: O'Brien
authors.affiliation: NIHR Health Protections Research Unit in Gastrointestinal Infections, University of Oxford, Oxford, UK. mara.violato@dph.ox.ac.uk.|Health Economics Research Centre, University of Oxford, Oxford, UK. mara.violato@dph.ox.ac.uk.
authors.forename: Mara
authors.initials: M
authors.lastname: Violato
authors.affiliation: NIHR Health Protection Research Unit in Gastrointestinal Infections, University of Liverpool, Liverpool, L69 7BE, UK. mmw@liverpool.ac.uk.|Department of Public Health and Policy, University of Liverpool, Liverpool, UK. mmw@liverpool.ac.uk.
authors.forename: Margaret
authors.initials: M
authors.lastname: Whitehead
mesh_terms: D019049:Developed Countries; D005767:Gastrointestinal Diseases / Q000150:complications*; D054624:Health Status Disparities; D006801:Humans; D007239:Infections / Q000150:complications*; D012923:Social Class; D012959:Socioeconomic Factors; D000078202:Systematic Reviews as Topic