Stock-out severity index: tool for evaluating inequity in drug stock-outs

The United Nations (UN) urged acceleration efforts to tackle inequity through its Sustainable Development Goals set in 2015. The need for focusing on equity has been highlighted in the field of public health for improved health outcomes. Drug stock-outs at the last mile is a complex challenge that hinders the efforts of equitable pharmaceutical access and availability. Severity experienced due to drug stock-outs are not equal among a group of mutually exclusive and collectively exhaustive populations. This paper proposes the stock-out severity index (SSI) to measure severity due to availability of drugs or lack thereof by incorporating risk factors and determinants of health from a combination of data sources. The spread of inequity among these groups of populations can be measured using the mean absolute deviation or the GINI coefficient on the SSI assigned to each population group. The paper demonstrates how the SSI can help define priority levels of varying population groups, rather than making decisions solely from an equality perspective that assumes uniformity across populations. It also demonstrates the impact on rearranging the priorities when the SSI is used. The paper presents guidelines for incorporating and implementing the SSI.