In this age of algorithms, how do we ensure clinical care is both science based and personalized? In this interview, Dr. Ryan Metcalf, section chief of Transfusion Medicine at ARUP Laboratories and University of Utah Health and associate professor of Pathology at the University of Utah School of Medicine, shares the story behind the new platelet transfusion guideline from the Association for the Advancement of Blood and Biotherapies (AABB). He describes how the authors addressed patient-specific variation and the inherent uncertainty of scientific evidence.