Unsafe medical care is a major source of disabling injuries and death throughout the world. The failure to notify, follow up, and action critical results, which signify life threatening situations, is of particular concern and may cause avoidable morbidity and mortality. International accreditation standards require pathology laboratories to have a system for the timely and reliable communication of critical results to clinical personnel responsible for patient care. In response, various practices and a number of different terminologies have been described in the literature. Increased attention to patient safety standards and multinational surveys, however, highlighted shortcomings and inefficiencies in existing communication systems. These failures and variations in practice call for clear guidance and harmonization of approaches in order to improve communications and to provide safer patient care. The objectives of this review are to create a harmonized terminology and to learn from international practices by systematically reviewing the best available evidence on existing approaches. Based on literature review findings we highlight key areas where harmonization is necessary and feasible and offer a conceptual framework and methods for designing better and more evidence-based systems for the timely notification of laboratory results that represent potential patient safety hazards.