The shift to personalized medicine, which supports medical treatment tailored to individual patient characteristics, has been hindered by uncertainty over the value, accuracy and clinical utility of companion diagnostic tests. Even for the handful of drugs approved by the Food and Drug Administration with labeling that links prescribing to specific biomarker measures, health plan operators, providers and payers frequently question the need to cover the added testing, according to analysis by Joshua Cohen of the Tufts Center for the Study of Drug Development (CSDD). Cohn noted at a recent CBI conference on “Precision Medicine and Companion Diagnostics” that only a few therapies have been approved by FDA with co-developed tests to inform prescribing; several more drugs gain links to specific diagnostics post-approval.