APPENDIX C: BIODOSIMETRY

Clinical signs and symptoms are dose dependent. Therefore knowing early markers to estimate radiation dose in radiologically exposed patients can be very helpful. Radiation dose can be estimated using time to emesis, medical history, and serial blood cell counts. Medical history should include the circumstances of suspected exposure, location relative to the incident, sheltering, and any other pertinent exposure details, such as smell or taste of dust/smoke and dust/debris on skin, in addition to clinical symptoms.

If laboratory support is available, serial complete blood counts (CBC) are one of the most readily available and useful methods to characterize dose received. An initial CBC with differential followed by serial measurements three times a day for 2 to 3 days will facilitate determination of the slope of lymphocyte depletion. A drop in lymphocyte count by more than 50% in the first 48 hours indicates a potentially lethal exposure. If there was only exposure to ionizing radiation, time to emesis can be used in the absence of laboratory support or as an adjunct to lymphocyte count. Emesis within 1 to 2 hours of exposure carries a poor prognosis.

Early-phase signs and symptoms
Dose estimates using blood lymphocyte cytogenetic biodosimetry

The chromosome-aberration cytogenetic bioassay (specifically lymphocyte dicentrics) is considered the gold standard in estimating dose. However, samples must be obtained after 24 hours of exposure, and results may not be available for 2 to 3 days, so time to emesis and lymphocyte counts remain the most useful tools in the initial assessment period. It is helpful to remember that if an individual has not vomited within 8 to 10 hours of exposure, it is unlikely he or she was exposed to a dose over 1 Gy. The Armed Forces Radiobiology Research Institute Biodosimetry Assessment Tool is a software package that can help providers assess exposure and guide therapy. The tool has a complimentary package for first responders called the First Responders Radiological Assessment Triage. These useful tools can facilitate optimization of a standardized framework for the response to nuclear or radiological incident.

The Department of Health and Human Services Radiation Emergency Management (REMM) webpage has interactive tools to assist with biodosimetry. These tools can be found at: https://remm.hhs.gov/ars_wbd.htm .