Last updated at 21:21 01 April 2007

Scientists have developed a simple method of converting blood from one group to another.

The breakthrough could mean the end of transfusion shortages by boosting supplies of group O negative blood.

This is known as 'universal' because it can be given to people of any group and is in high demand for emergencies. Giving patients the wrong blood can result in a severe immune reaction and even death.

Writing in the journal Nature Biotechnology, an international team of researchers described how they converted blood from group A, B or AB to group O.

Blood is classified according to the sugar molecules, antigens, on the surface of red cells. A damaging immune response can be triggered if a patient receives blood from a group carrying a different molecule to their own.

The scientists, led by Professor Henrik Clausen from the University of Copenhagen in Denmark, used bacterial enzymes as biological 'scissors' to cut out the sugar molecules in only an hour. This effectively changed the blood to antigen-free Group O.

Trials with patients will now take place before such converted blood is used in hospitals.