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which is revised over time as more clinical and dosimetric data become available (Table
6.4).
Rapid diagnosis. The initial diagnosis provides an initial determination of dose that
guides early treatment. Diagnostic steps can begin in an emergency department, in any
acute-care setting, or even at a field hospital. The best and quickest diagnostic indicators
are:
• The time to onset of vomiting (prodrome).
• The speed of lymphocyte depletion (serial lymphocyte counts).
The time to onset of vomiting provides an estimate of the prodrome and suggests a dose
range. The clinician should then observe the onset and duration of the subsequent latency.
These various times combine to provide an estimate of dose, which suggests a treatment
plan (Table 6.5). For example, prodromal symptoms of vomiting that began 1–2 hours
after exposure, with duration of approximately 24 hours, suggests radiation exposure in
the range of 3–5 Gy (Table 6.6).
The most useful early laboratory test is the CBC, including an absolute WBC count.
WBC counts should be performed every 6-8 hours during the first day after exposure and
at least daily thereafter for the next week. Lymphocyte counts are the best rapid gauge of
dose. The classic Andrews diagram for lymphocyte depletion curves (Figure 6.6) was
published in 1965 and is still useful. Lymphocyte counts drop quickly with high radiation
doses. A drop of 50% or more in 24 hours indicates a severe radiation injury.
Later diagnostic data. Later diagnostic data help to refine both the estimate of dose and
the treatment plan. Data that should be gathered over time include physical dosimetry,
biodosimetry, and clinical physical findings. These data should be recorded for all
patients, regardless of symptoms or estimated level of exposure. Such group data may be
crucial to clinical evaluation of individuals within the group. These data can also provide
a pattern of illness for the group, which can lead to changes in the estimate of dose or
even the diagnosis.
Physical dosimetry. The dose assessment method most familiar to medical personnel is
physical dosimetry. This can be used for victims who wore a personal dosimeter (e.g., a
film badge), thermoluminescent device (TLD), or pocket ionization chamber. However, it
is unlikely that civilians—or even most police, firefighters, and military personnel—will
have worn dosimeters. It is also important to remember that dosimeters can be damaged
during the radiation event, rendering them unreliable. Therefore, clinicians should request
dosimetric data from emergency response agencies or military units with trained
technicians. Such specialized personnel may be able to estimate dose using radiation
detection, indication and computation (RADIAC) equipment and isotope counters.
Biodosimetry. Biodosimetry can provide a good estimate of dose but requires specialized
testing. This is performed at a few national centers, including AFRRI in Bethesda, MD,
and the Radiation Emergency Action Center Training Site (REAC-TS) in Oak Ridge, TN.
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