They identified a total of 170 microRNAs in the blood and showed that a small number of them strongly changed with radiation exposure and thereby can act as a "signature" of radiation dose.

Mice exposed to two radiation doses, one lethal and one survivable, showed no outward differences for three to four weeks. But using the microRNA signature, the researchers were able to predict within 24 hours which animals would survive.

In experiments using "humanized" mice who received transplants of human bone marrow to promote recovery, those exposed to lethal doses of radiation also revealed the same microRNA signatures, leading the researchers to believe the test would similarly work in humans.

When the researchers gave the mice a radiation protection drug that "rescued" many of the human cells, the microRNA test results confirmed its protective effect.

"Our data suggest that serum (microRNAs) can serve as functional dosimeters of radiation, representing a potential breakthrough in early assessment of radiation-induced hematopoietic damage," the researchers concluded.