title: The measurement of household socio-economic position in tuberculosis prevalence surveys: a sensitivity analysis.
abstract: OBJECTIVE
  To assess the robustness of socio-economic inequalities in tuberculosis (TB) prevalence surveys.
  
  
  METHODS
  Data were drawn from the TB prevalence survey conducted in Lusaka Province, Zambia, in 2005-2006. We compared TB socio-economic inequalities measured through  an asset-based index (Index 0) using principal component analysis (PCA) with those observed using three alternative indices: Index 1 and Index 2 accounted respectively for the biases resulting from the inclusion of urban assets and food-related variables in Index 0. Index 3 was built using  regression-based analysis instead of PCA to account for the effect of using a different assets weighting strategy.
  
  
  RESULTS
  Household socio-economic position (SEP) was significantly associated with prevalent TB, regardless of the index used; however, the magnitude of inequalities did vary  across indices. A strong association was found for Index 2, suggesting that the exclusion of food-related variables did not reduce the extent of association between SEP and prevalent TB. The weakest association was found for Index 1, indicating that the exclusion of urban assets did not lead  to higher extent of TB inequalities.
  
  
  CONCLUSIONS
  TB socio-economic inequalities seem to be robust to the choice of SEP indicator. The epidemiological meaning of the different extent of TB inequalities is unclear. Further studies are needed to confirm our conclusions.
authors.affiliation: Faculty of Epidemiology and Population Health, Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, London, UK. delia.boccia@lshtm.ac.uk
authors.forename: D
authors.initials: D
authors.lastname: Boccia
authors.forename: J
authors.initials: J
authors.lastname: Hargreaves
authors.forename: L D
authors.initials: LD
authors.lastname: Howe
authors.forename: B L
authors.initials: BL
authors.lastname: De Stavola
authors.forename: K
authors.initials: K
authors.lastname: Fielding
authors.forename: H
authors.initials: H
authors.lastname: Ayles
authors.forename: P
authors.initials: P
authors.lastname: Godfrey-Faussett
mesh_terms: D005191:Family Characteristics; D006306:Health Surveys / Q000592:standards*; D006801:Humans; D015995:Prevalence; D012680:Sensitivity and Specificity; D012959:Socioeconomic Factors; D014376:Tuberculosis / Q000453:epidemiology*