Strategies of stratification: Regulating market access in the era of personalized medicine.

Personalized medicine raises the stakes of pharmaceutical market regulation. Drawing on pragmatist valuation studies and science and technology studies literature on personalized medicine and pharmaceutical markets, this article demonstrates how complex negotiations about the value of a pharmaceutical can constitute a market in various ways, while also shaping the concerned patient populations. Tracing the path of a pharmacogenetic treatment, Spinraza, from its approval by the European Medicines Agency to its adoption in the publicly funded Danish healthcare system, we show how the market was formatted through particular stratifications of the patient population. We conceptualize these seemingly technical moves as strategies of stratification, that is, the application of techniques to assemble and divide data - and what data are meant to represent - into groups delineated by certain characteristics. We argue that stakeholders' use of strategies of stratification has important implications not only for market access, but also for the delineation of diseases and patient populations. Hence, it is crucial to make intelligible the mutual constitution of pharmaceutical markets and patient populations and the political efforts of delineating and connecting the two.