Substandard and falsified medicines: proposed methods for case finding and sentinel surveillance.

UNSTRUCTURED: Background: The World Health Organization and others warn that substandard and falsified medicines harm health and waste money, especially in low and middle income countries. However, no country has measured the extent of the problem market-wide, and no agreed methods exist to estimate prevalence of either substandard or falsified medicines. This is in part because the task seems overwhelming; medicine markets are huge and diverse, and testing medicines is expensive. Many countries do operate some form of post-market surveillance of medicines, but their methods and goals differ. There is currently no clear guidance on which surveillance method is most appropriate to meet any specific public health goal. Objective: In this Viewpoint, we discuss the utility of both case finding and risk-based sentinel surveillance for substandard and falsified medicines, linking each to specific public health goals. We posit that choosing the system most appropriate to the goal, and implementing it with a clear understanding of the factors driving the production and sale of substandard and of falsified medicines, will allow for surveillance resources to be concentrated most efficiently. Proposed methods: We adapt principles used for disease outbreak response to suggest a case-finding system that uses secondary data to flag poor quality medicines, proposing risk-based indicators that differ for substandard and for falsified medicines. This system potentially offers a cost-effective way of identifying "cases" for market withdrawal, enhanced oversight, or other immediate response. We further propose a risk-based sentinel surveillance system which concentrates resources on measuring the prevalence of substandard and falsified medicines in risk clusters in which they are most likely to be found. The sentinel surveillance system provides base data for a transparent, spreadsheet-based model for estimating the national prevalence of substandard and falsified medicines. The methods we propose are based on ongoing work in Indonesia, a large and diverse middle-income country currently aiming to achieve Universal Health Coverage. They are designed to be adaptable to other resource-constrained settings.