The San Francisco Chronicle
FDA Precaution a Bad Idea
Disease risk doesn't justify ban on blood donors
by Howard Fienberg
Tuesday, July 27, 1999

IMAGINE THIS scenario: Your child needs a blood transfusion, fast. But the doctor informs you the blood is not available. A shortage exists because many donors have been turned away and stockpiles disposed of --precautionary measures to protect the blood supply from the risk of infection from a poorly understood disease that might or might not be transmitted by blood. Unfortunately, this scenario is not just hypothetical.

Very soon, the nation's already short blood supply may be reduced further because a remote risk -- infection by the human version of mad cow disease (nvCJD) -- has taken precedence in health policy.

No trace of the disease has ever been found in the United States. But travelers to Britain (22 percent of blood donors, according to a recent Red Cross survey) just might have consumed contaminated beef, which just might cause nvCJD in humans, which just might be conveyed via their bloodstream into the American blood pool, which just might lead to infection in people who need transfusions. Too much of a chance to take, apparently.

The nation's blood supply has dropped alarmingly. ``I have never seen a situation like we have today,'' said Alfred Grindon, medical director for the American Red Cross. Blood donation traditionally drops in the summer, but the U.S. blood supply is continuously near the bottom of the barrel. Although 60 percent of the population is eligible to donate blood, only about 5 percent do, according to Karen Eisele of the Red Cross.

Now the Food and Drug Administration (FDA) plans to ban Americans who have spent more than six months in Britain since 1980 from donating blood, eliminating at least 1 in every 45 donors. Has the FDA made a sound trade-off of risk? The journal Nature noted that no cases of nvCJD ``have ever been attributed to blood or a blood product since the new variant disease was identified.'' Dr. Adriano Aguzzi of Zurich University says ``research has certainly not proven that blood is infectious.'' And a special council of the American Medical Association reported last month that ``epidemiological studies show no evidence that transmission can occur through blood.''

So is there any risk? If so, it is incredibly low: Fewer than 50 people out of 50 million beef-eating Britons have demonstrated symptoms of the disease. There is no way of knowing if there were only a few more people incubating nvCJD, or if an entire beef-eating population might be set to succumb. If the disease lives up to its media billing, these 40-some victims could just be the tip of the iceberg. However, Professor John Pattison, chairman of Britain's Spongiform Encephalopathy Committee, said last year that nvCJD should afflict only between 100 and 1,500 people -- making it a relatively small health threat. Because the risk of nvCJD to the blood supply is theoretical, deciding who should be barred from donating blood becomes problematic.

With the bovine version of mad cow disease now nearly eliminated from the British landscape, when can we mark a cut-off for the risk? Portugal was recently pummeled for the spread of mad cow disease in its cattle, and British beef was consumed outside of Britain. Should we perhaps ban donors who have been anywhere outside North America? The precautionary principle, invoked to justify destroying a significant part of the nation's blood cache, dictates that it is better to be safe than sorry. But risks must be balanced. Rejecting one risk tends to present a half dozen others in its place.

According to Richard Davey, chief medical officer for the American Red Cross, ``It's likely . . . that taking this step in the face of a theoretical risk may actually decrease the safety of the blood supply.'' The National Blood Data Resource Center notes that demand for blood is increasing by 1 percent per year, while donations are decreasing at nearly the same rate. New donors to fill the gap could carry diseases more definitively risky than nvCJD. But more importantly, finding those replacement donors is likely to be difficult.

This summer, Canada intends to begin leukoreduction -- the filtering of white blood cells. It could prevent the spread of nvCJD if the theory that it spreads by white blood cells were correct. While expensive, leukoreduction has a wide range of other transfusion benefits. If used in the United States, it would negate the need for any donor ban. The FDA faces some hard questions. In particular, is the risk of a blood shortage better than potentially bad blood?

Howard Fienberg is a research analyst with the Statistical Assessment Service a nonpartisan, nonprofit research organization in Washington, D.C.

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