Using multiple measures to assess changes in social inequalities for breast cancer screening

Objectives: To identify changes in social inequalities for mammograms uptake in Belgium over the period 1997–2008 using multiple indices, and to assess the contribution of the national breast cancer screening programme in these changes. Methods: Data were obtained from four waves of the Belgian Health Interview Survey. The socio-economic position was defined by the educational level. Inequalities were measured both with pairwise measures comparing extreme educational groups (prevalence difference and prevalence ratio), and with indices measuring the total inequality impact at population level: the Population Attributable Fraction (PAF), the Relative Index of Inequality (RII) and the Slope Index of Inequality (SII). Results: All indices show a substantial decrease in inequalities in mammographic uptake between 1997 and 2008. For the indices of total impact (PAF, RII, SII), the change occurred between the first two waves (1997 and 2001) and stabilized afterwards, while for pairwise indices the evolution continued over the whole period. Conclusion: Using multiple indices of inequality is necessary for a more complete understanding of the changes: total impact inequality indices should always complement simple pairwise measures. The inequalities in mammograms uptake, as measured with total impact indices, only decreased before the start of the national screening programme.