At 100 Rads of acute total body exposure, significant hematologic responses begin to appear. These changes can be very useful in estimating the exposure to the patient if no film badges or dosimetry was present at the accident.
The lymphocytes are the most sensitive cells to the effects of radiation. Changes can be seen as early as several hours post exposure. It is for this reason that the lymphocytes are termed a "biologic dosimeter." The levels of lymphocytes drop quickly to approximately 60% of the previous circulating value and then slowly recover over the next six months.
The neutrophils gradually decrease to 70% of their previous value over a period of 45 days post exposure and then recover gradually over the next several months. The platelets fall to 60% of their prior circulating value. The peak effect is seen at 30 days post exposure.
Despite the noticible decreases in the above circulating cells, there is no increase in infection or bleeding as a result.