LONDON, England (CNN) -- Eighteen British service personnel who received transfusions of U.S. military blood in Iraq and Afghanistan are undergoing tests for infections and diseases because the blood may not have been properly screened, the British government said Thursday.
The Ministry of Defense said the service members received emergency life-saving transfusions in U.S. medical facilities on the front lines between 2001 and 2007. The transfusions were delivered "live," or directly from one person to another.
It said the risk of infection was low, and the service members were being screened as a precaution.
"These 18 people would almost certainly have died without receiving the emergency transfusions of blood at the front line," said Derek Twigg, Britain's undersecretary of state for defense.
The ministry said the U.S. and Britain retrospectively screen samples of donated blood to check that the live transfusions are safe, but that did not necessarily happen with the blood given to the British service personnel.
"The MoD has identified that a small number (18) of UK service personnel might have received blood or blood products from U.S. emergency donor panels that might not have had a valid retrospective test," the ministry said in a statement.
"Without a valid retrospective test, there is a small risk that an emergency blood transfusion could transfer blood-borne diseases from the donor to the recipient without being detected," it said.
There have been instances during military operations in Iraq and Afghanistan "where fresh whole blood and platelets have been collected and transfused in the field to meet the need of physicians dealing with multiple and highly severe trauma cases," the Department of Defense said in a written statement.
"These blood products are not tested in the field per U.S. Food and Drug Administration standards due to the need for rapid transfusions to save life.
"Under these circumstances, an emergency blood transfusion was the only way of saving the lives of gravely wounded UK personnel.
"For most patients in U.S. military hospitals, FDA-licensed blood is all that is used for their trauma care," the department said.
A defense ministry spokesman said the issue came to light during the first week of November, when U.S. officials notified their British counterparts of the potential problem.
"The (U.S. Defense Department) has told us that for the British service personnel they have records for, they know that the blood that they received is clean. However they do admit that their records are incomplete," the spokesman said.
The ministry said it had contacted everyone whose transfusion may have been contaminated, but urged any other service member with concerns about the transfusion they received while deployed to contact their doctor. E-mail to a friend