Researchers in the United States have found that adding small amounts of citric acid to blood plasma produces four times as much Factor VIII as normal.

Factor VIII plays a crucial role in blood clotting and is used to treat patients with haemophilia.

Citric acid seems to act as a 'primer', allowing for more of these factors to be harvested from the plasma

John Owens, University of California Irvine

In recent years, however, hospitals in the US and Europe have reported shortages of the product because of manufacturing and other problems. There are also major shortages in the developing world.

But John Owens and colleagues at the University of California Irvine believe they may have found a way to overcome this problem.

Key proteins

They found that adding citric acid to blood plasma helped them to harvest more of key proteins like Factor VIII.

The process also enabled them to produce more of other blood proteins such as fibrinogen and von Willebrand's Factor which are used in surgery.

Overall, they managed to yield four times as much of these proteins from the plasma than they would normally.

"We believe that citric acid seems to act as a 'primer', allowing for more of these factors to be harvested from the plasma," said Mr Owens.

"Citric acid not only helped produce higher levels of these factors but also produced high levels of other proteins important in surgical procedures."

The researchers said the discovery could be "an inexpensive and safe way" to produce these agents and to overcome recent supply problems.

Dr David Keeling of the UK's Oxford Haemophilia Centre welcomed the findings.

"If we can get more Factor VIII it would be good. This plasma-derived Factor VIII would be cheaper and it would also help to tackle shortages in the developing world," he told BBC News Online.

The findings of the study were presented to the Congress of the International Society of Blood Transfusion in Vancouver, Canada.