U.S. researchers said Wednesday they have developed a novel blood test that could predict whether radiation exposure in a nuclear accident like Japan's Fukushima disaster will eventually be fatal within the first 24 hours.

Using such a test could \"facilitate timely medical intervention and improve overall survival of exposed individuals，\" according to their paper， which was published in the U.S. journal Science Translational Medicine.

Exposure to high-energy radiation from nuclear power plants， radioactive material， nuclearweapons， and other sources can damage different organs and lead to cancer and infection.

Injury from radiation， however， can take weeks or months to appear， and existing techniques do not effectively predict the severity of injury sustained， they said.

\"After a radiation release， there is currently no way to tell who was exposed and who wasn't， andif someone was exposed， is it lethal or not？\" senior author Dipanjan Chowdhury of Boston-based Dana-Farber Cancer Institute said in a statement.

Drugs that can limit bone marrow damage are available but， to be effective， must be given befor the appearance of radiation symptoms， Chowdhury noted.

In their study， the researchers focused on microRNAs， small RNAs that help regulate geneactivity. These molecules are made in cells， but some are found in the bloodstream， and there searchers asked whether varying doses of radiation might cause corresponding changes in microRNAs in the blood.

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.

http：//www.chinadaily.com.cn/life/2015-05/18/content_20746570.htm