title: The association between household socioeconomic position and prevalent tuberculosis in Zambia: a case-control study.
abstract: BACKGROUND
  Although historically tuberculosis (TB) has been associated with poverty, few analytical studies from developing countries have tried to: 1. assess the relative impact of poverty on TB after the emergence of HIV; 2. explore the causal mechanism underlying this association; and 3. estimate how many cases of TB could be prevented by improving household socioeconomic position (SEP).
  
  
  RESULTS
  We undertook a case-control study nested within a population-based TB and HIV prevalence survey conducted in 2005-2006 in two Zambian communities. Cases were defined as persons (15+ years of age) culture positive for M. tuberculosis. Controls were randomly drawn from the TB-free participants enrolled in the prevalence survey. We developed a composite index of household SEP combining variables accounting for four different domains of household SEP. The analysis of the mediation pathway between household SEP and TB was driven by a pre-defined conceptual framework. Adjusted Population Attributable Fractions (aPAF) were estimated. Prevalent TB was significantly associated with lower household SEP [aOR = 6.2, 95%CI: 2.0-19.2 and aOR = 3.4, 95%CI: 1.8-7.6 respectively for low and medium household SEP compared to high]. Other risk factors for prevalent TB included having a diet poor in proteins [aOR = 3.1, 95%CI: 1.1-8.7], being HIV positive [aOR = 3.1, 95%CI: 1.7-5.8], not BCG vaccinated [aOR = 7.7, 95%CI: 2.8-20.8], and having a history of migration [aOR = 5.2, 95%CI: 2.7-10.2]. These associations were not confounded by household SEP. The association between household SEP and TB appeared to be mediated by inadequate consumption of protein food. Approximately the same proportion of cases could be attributed to this variable and HIV infection (aPAF = 42% and 36%, respectively).
  
  
  CONCLUSIONS
  While the fight against HIV remains central for TB control, interventions addressing low household SEP and, especially food availability, may contribute to strengthen our control efforts.
authors.affiliation: Faculty of Epidemiology and Population Health, Department of Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, London, United Kingdom. Delia.Boccia@lshtm.ac.uk
authors.forename: Delia
authors.initials: D
authors.lastname: Boccia
authors.forename: James
authors.initials: J
authors.lastname: Hargreaves
authors.forename: Bianca Lucia
authors.initials: BL
authors.lastname: De Stavola
authors.forename: Katherine
authors.initials: K
authors.lastname: Fielding
authors.forename: Ab
authors.initials: A
authors.lastname: Schaap
authors.forename: Peter
authors.initials: P
authors.lastname: Godfrey-Faussett
authors.forename: Helen
authors.initials: H
authors.lastname: Ayles
mesh_terms: D000293:Adolescent; D000328:Adult; D016022:Case-Control Studies; D006801:Humans; D008875:Middle Aged; D015995:Prevalence; D012307:Risk Factors; D012923:Social Class; D014376:Tuberculosis / Q000453:epidemiology*; D015024:Zambia / Q000453:epidemiology