The inverse equity hypothesis: Does it apply to coverage of cancer screening in middle-income countries?

Background It is uncertain whether the inverse equity hypothesis-the idea that new health interventions are initially primarily accessed by the rich, but that inequalities narrow with diffusion to the poor-holds true for cancer screening in low and middle income countries (LMICs). This study examines the relationship between overall coverage and economic inequalities in coverage of cancer screening in four middle-income countries. Methods Secondary analyses of cross-sectional data from the WHO study on Global Ageing and Adult Health in China, Mexico, Russia and South Africa (2007-2010). Three regression-based methods were used to measure economic inequalities: (1) Adjusted OR; (2) Relative Index of Inequality (RII); and (3) Slope Index of Inequality. Results Coverage for breast cancer screening was 10.5% in South Africa, 19.3% in China, 33.8% in Russia and 43% in Mexico, and coverage for cervical cancer screening was 24% in South Africa, 27.2% in China, 63.7% in Mexico and 81.5% in Russia. Economic inequalities in screening participation were substantially lower or non-existent in countries with higher aggregate coverage, for both breast cancer screening (RII: 14.57 in South Africa, 4.90 in China, 2.01 in Mexico, 1.04 in Russia) and cervical cancer screening (RII: 3.60 in China, 2.47 in South Africa, 1.39 in Mexico, 1.12 in Russia). Conclusions Economic inequalities in breast and cervical cancer screening are low in LMICs with high screening coverage. These findings are consistent with the inverse equity hypothesis and indicate that high levels of equity in cancer screening are feasible even in countries with high income inequality.