A catastrophic event such as a nuclear device detonation in a major U.S. city would cause a mass casualty with millions affected. Such a disaster would require screening to accurately and effectively identify patients likely to develop acute radiation syndrome (ARS). A primary function of such screening is to sort the unaffected, or worried-well, from those patients who will truly become symptomatic. This paper reviews the current capability of high-accuracy biodosimetry methods as screening tools for populations and reviews the current triage and medical guidelines for diagnosing and managing ARS. This paper proposes that current triage categories, which broadly categorize patients by likelihood of survival based on current symptoms, be replaced with new triage categories that use high-accuracy biodosimetry methods. Using accurate whole-body exposure dose assessment to predict ARS symptoms and subsyndromes, clinical decision-makers can designate the appropriate care setting, initiate treatment and therapies, and best allocate limited clinical resources, facilitating mass-casualty care following a nuclear disaster.