PURPOSE: This workshop will describe the methods and considerations required when performing health technology assessment of prognostic and diagnostic tools. Participants will learn how the appraisal process differs from that applied to healthcare interventions, and how it relates to the wider literature on heterogeneity, stratified decision making and personalized health care. Participants will also see how cost-effectiveness analysis can be used to optimize diagnostic tools. DESCRIPTION: Prognostic and diagnostic tools give information on disease status (diagnosis) and factors that determine levels of risk for future health outcomes and/or response to treatment. Their value is dependent on the net health benefits from targeting treatment on the basis of the information acquired; they have value insofar as they identify subgroups of patients for whom different decisions can be taken. Cost-effectiveness analysis can be used not only to determine whether such tools can improve population health, but also to determine the optimal prognostic or diagnostic criteria on the basis of net health benefit. The decision about how and whether to introduce a prognostic or diagnostic tool should integrate considerations about the value of the subsequent treatment pathway. Performing health technology assessment of prognostic and diagnostic technologies thus requires joint consideration of multiple components of value, which introduces additional challenges compared to the more routine assessment of a single technology in isolation. Audience members will be asked their experience, whether the proposed framework or case study have helped to address any challenges and where further methodological development is required. Manuel Espinoza will chair and facilitate audience participation. Marta Soares will describe a framework for the health technology appraisal of prognostic and diagnostic tests. Susan Griffin will describe the use of cost-effectiveness analysis to optimize the blood glucose threshold for diagnosing gestational diabetes. Andy Briggs will discuss the wider context of value of heterogeneity and personalized healthcare.