Socio-economic gradients in prevalent tuberculosis in Zambia and the Western Cape of South Africa.

OBJECTIVE: To describe the associations between socio-economic position and prevalent tuberculosis in the 2010 ZAMSTAR Tuberculosis Prevalence Survey, one of the first large tuberculosis prevalence surveys in Southern Africa in the HIV era. METHODS: The main analyses used data on 34 446 individuals in Zambia and 30 017 individuals in South Africa with evaluable tuberculosis culture results. Logistic regression was used to estimate adjusted odds ratios for prevalent TB by two measures of socio-economic position: household wealth, derived from data on assets using principal components analysis, and individual educational attainment. Mediation analysis was used to evaluate potential mechanisms for the observed social gradients. RESULTS: The quartile with highest household wealth index in Zambia and South Africa had, respectively, 0.55 (95% CI 0.33-0.92) times and 0.70 (95% CI 0.54-0.93) times the adjusted odds of prevalent TB of the bottom quartile. College or university-educated individuals in Zambia and South Africa had, respectively, 0.25 (95% CI 0.12-0.54) and 0.42 (95% CI 0.25-0.70) times the adjusted odds of prevalent TB of individuals who had received only primary education. We found little evidence that these associations were mediated via several key proximal risk factors for TB, including HIV status. CONCLUSION: These data suggest that social determinants of TB remain important even in the context of generalised HIV epidemics.