This commentary by Josephine Exley and Tanya Marchant, published in BMJ Global Health reviews methodological constraints that limit measuring inequalities in effective coverage when using only population-based data and linked population and health facility data.
When using population-level data alone, the authors find that quality dimensions of health provider practise are not incorporated. Information on socio-demographic and economic variables is typically captured in household surveys. These, however don’t provide information on inputs and evidence on the validity of coverage data collected through household surveys. It is therefore necessary to link multiple data sources.
For many services effective coverage measurement relies on linking data on access to care, derived from household surveys, where measures of inequality are incorporated, with information on the quality of care from health facility datasets. Health facility data assume that there are no systematic differences in the quality of care between individuals attending the same facility. However, evidence demonstrates that this is not the case; individuals with different characteristics receive different quality of care.
The authors point out that this is exactly where measurement issues arise. Relying on summary facility measures for linked effective coverage ignores variation in quality of care both within and between facilities. While generating effective coverage measures using only household data limits the adjustment made for quality and introduces issues with the reliability and
validity of measures.
Effective coverage measures remain a crucial tool as we move towards universal access to high-quality care and there is interest to understand inequalities in effective coverage; however, the authors caution, we need to acknowledge that the data sources used for effective coverage measures can only partially reflect inequalities.
Alongside continuing to promote effective coverage, there is a need to support the adoption of unique health identifiers that would allow linking information on individuals’ care-seeking with information on the quality of care received.
In the meantime, greater advocacy and investment in health information systems is needed to shift from reporting aggregated-level to individual-level data and to capture information on individual patients that would enable examination of inequalities within facilities.
