Plasma Iodine131 Levels as Diagnostic Tests for Lethal X-Radiation Exposure in Rats

By determining plasma levels of trace amounts of radio-iodine in rats 24 hours after injection and 72 hours after x-ir-radiation with 0 to 900 r, it was possible to divide the animals into sublethal and lethal exposure groups with an accuracy of 83 to 95%, depending on whether a false diagnosis of lethal exposure is acceptable. There appeared to be a reversal of the effect on I131 level at doses in excess of 900 r, which might be of value in triage. At these dose levels, the diagnosis of severe radiation injury was obvious from the appearance of the animals and the combined clinical impression of severe damage and a negative I131 test might facilitate the diagnosis of supralethal exposure.