Bloody Risks

by Howard Fienberg
September 9, 2000

The U.S. Food and Drug Administration (FDA) and Red Cross plan to further tighten their rules on who can donate blood. Both aim to ensure the safety of our blood supply, but seem unable to balance competing risks. Blinded by fears that infection by the human version of mad cow disease, new variant Creutzfeldt Jakob disease (nvCJD), might spread through blood, they have neglected the problem of a shrinking blood supply which their regulations exacerbate. In their rush to ensure blood safety, they risk leaving us no blood at all.

No trace of nvCJD has ever been found in the United States. But travelers to Western Europe 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.

Last year, the Food and Drug Administration (FDA) banned Americans who have spent more than six months in Britain between 1980 and 1996 from donating blood, eliminating 2.2 percent of eligible donors. Now, the FDA proposes to extend the ban to those who were in Britain for more than three months and those whom have spent at least five years in Europe since 1980. The Red Cross goes farther, placing their ban on any donors having spent more than six months in Europe. The FDA expects its guidelines to eliminate about five percent of eligible donors; the Red Cross, eight percent.

Are we making a sound risk trade-off? There is no evidence that nvCJD can spread via blood transfusion. Indeed, a special council of the American Medical Association concluded two years ago that "epidemiological studies show no evidence that transmission can occur through blood." Further, while most researchers agree that mad cow disease is linked to nvCJD, they do not know how it is transmitted. Does it take one mad cow-infected hamburger or years of continuous beef-eating? We have no clue. So what do we do about Americans who consumed British beef before it was banned in 1989? Do we arbitrarily assume that they did not eat enough?

Overall, if there is any risk, it is probably low. About 110 people have died from nvCJD. If the disease lives up to its media hype, these victims could just be the tip of the iceberg. But an Oxford University research team projected last year that the maximum number of Britons who could be afflicted with nvCJD must be less than 139,000, and there could be as few as one hundred or less cases. While these are only projections, they depict a relatively limited threat to public health.

If the risk of nvCJD to the blood supply is theoretical, how can we decide whom to bar from donating blood? With the bovine version of mad cow disease almost eliminated from the British landscape, when can we mark a cut-off for the risk there? The most recent FDA and Red Cross proposals were spurred by small outbreaks of mad cow across Europe this past winter, but what happens when mad cow cases hit other countries? Should we then 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 others in its place.

Richard Davey, former chief medical officer for the American Red Cross, was critical of the last decision on British blood donors: "It's likely ... that taking this step in the face of a theoretical risk may actually decrease the safety of the blood supply." The nation's blood supply is in a continual crisis. On the demand side, more surgeries and an ever-graying populace lead to increasing demand. Meanwhile, on the supply side, although some 60 percent of Americans are eligible to donate blood, only about 5 percent do. According to Michael Busch of the Blood Centers of the Pacific, the proposed bans target older, well-traveled donors, who are among our most reliable. New donors are hard to find and expensive to recruit. They are also more likely than current donors to carry diseases more definitively risky than nvCJD.

Wary of repeating past mistakes with the blood safety, like the spread of AIDS, the FDA and Red Cross will take the route of caution. But caution should derive from a reasonable assessment of cost and benefit, not the arbitrary elevation of little-known risks to overwhelming importance. Both agencies face some tough questions. If a case of mad cow were one day found in the United States, would they then ban all blood donations (the U.K. has done so - it now imports its blood from the U.S.)? At what point will they draw the line between vague possibilities and concrete probabilities?

HOWARD FIENBERG is research analyst at the Statistical Assessment Service (STATS), a nonprofit nonpartisan think tank in Washington, D.C.

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