Bad Blood Between the FDA and Europe

A US proposal to ban the import of blood products from all European sources will further tax the already overburdened blood banks of the United States. These draconian measures are being suggested to prevent new variant Creutzfeldt Jakob Disease (nvCJD), a progressive, incurable, neurodegenerative disease, being transmitted to otherwise healthy individuals by contaminated blood. However, this plan to restrict the donor population is based not on hard, scientific evidence but on two unsupported fears: that thousands of Europeans are in a preclinical, undiagnosed state in the development of nvCJD and that nvCJD is transmitted by blood. The prevailing theory is that nvCJD is caused by ingesting meat contaminated with nervous tissue from cattle with the closely related disease, bovine spongiform encephelopathy (BSE, also called "mad cow disease"). About 100 people in the United Kingdom have contracted nvCJD. The current proposal to refuse blood from European donors stems from the fact that the United Kingdom, although worst hit by the BSE epidemic, is not the sole country with BSE-infected cattle. Ireland, France, Portugal, and Switzerland all have had hundreds of cattle diagnosed with BSE and many EU nations have imported some cattle that later were found to have BSE. In fact, nvCJD is also not limited to the United Kingdom; Ireland and France together have less than 10 cases. At present, the United States does not accept blood from people living in or who have spent significant amounts of time in the United Kingdom. An advisory panel to the Food and Drug Administration has recommended that blood be refused from all European sources and all those donors in the United States who have spent significant amounts of time in Europe. In an ideal world, the supply of blood products would vastly outstrip the need for blood and it would be justifiable to refuse blood from those donors that would pose any risk, no matter how insignificant, to the recipient. Blood transfusion itself is not without inherent risks, over the past decade in the United States several hundred people have died or become seriously ill due to mistakes or complications directly associated with receiving donated blood. Bacterial infections due to transfused blood claim dozens of lives each year and even simple mistakes, such as ABO incompatibility, kill hundreds more. The US supply of donated blood is far from plentiful. This summer, several non-emergency surgeries were postponed due to blood shortages. To meet the US need of blood, some blood banks turn to supplies from other countries; according to the New York Blood Center, 25 percent of blood used for transfusions in the New York metropolitan area is imported from Europe. Restricting the donor base in this manner would reduce the available supply of blood by 10 percent over the whole country with major coastal metropolitan areas being hardest hit. Therefore, the blood banks of New York and other cities will not be replenished by blood supplied by other parts of the United States. According to the New York Blood Center, if blood from European sources is deemed unacceptable for American recipients and no other source of blood is found, 200 of the thousands of life-saving transfusions per day will not occur in the greater New York area. By trying to protect Americans from blood-borne illness, the FDA will withhold lifesaving treatment from those who could otherwise be saved by blood that is almost assuredly safe. Regardless of the hardships placed on US blood banks, if it were proven that nvCJD could be transmitted via blood, then removing any donor potentially infected would be reasonable. However, no hard evidence exists that nvCJD can be transmitted by blood. There is abundant evidence supporting the conclusion that classical CJD, a closely related disease to nvCJD that is transmitted by contaminated surgical instruments or tissue grafts, is not transmitted by blood transfusions. Also, no hemophiliacs in the United Kingdom or elsewhere have contracted nvCJD, suggesting that there is little increased risk from accepting blood donations in the development of nvCJD. The blood factors that hemophiliacs receive are heat treated to reduce the risk of iatrogenic spread of infectious disease. However, prions are extremely stable under conditions that destroy most proteins such as heat treatment; therefore, the fact that no hemophiliacs have developed nvCJD is significant. Furthermore, a few patients are known to have accepted blood from individuals who later developed nvCJD and all of these patients remain healthy. The FDA points to an unfinished study in which sheep contracted scrapie (the sheep equivalent of BSE) after whole blood transfusions from unsymptomatic, scrapie-infected sheep. In this study, however, the sheep were chosen because they were genetically most susceptible to scrapie transmission. Furthermore, only one sheep contracted scrapie from the more than a dozen that were given a transfusion directly from an infected animal. Because this study is unfinished, no data on the scrapie status is available about the control sheep that did not get transfusions. Given that it is possible that scrapie spontaneously developed in sheep, it remains to be shown that the one, genetically predisposed sheep that developed scrapie after transfusion would not have developed scrapie without a transfusion. One worrisome fact is that unlike classical CJD, the infectious agent of nvCJD can be detected in tissues outside of the central nervous system, such as white blood cells. Almost all blood has the white blood cells removed before use. In fact, the blood used from European sources in the United States today is fractionated so that only purified red blood cells are kept, a cell type that has no detectable levels of nvCJD agent. By removing the cells that could potentially carry nvCJD to the recipient, the risk of transmission is greatly reduced. Furthermore, nvCJD is an extremely rare disease. Fewer than 10 people have ever been diagnosed with nvCJD in all of continental Europe (approximately 1:100,000,000 continental Europeans suffer from the disease). The rarity of nvCJD makes it extremely unlikely that any individual blood donor will carry nvCJD. The FDA advisory panel fears that the vast majority of those that will develop nvCJD are undiagnosed at the moment and the population of diseased individuals will explode over the coming years. However, current trends in the numbers of new nvCJD patients do not indicate exponential spread of nvCJD in the population and the amount of infected individuals is increasing only gradually. Even if the amount of nvCJD patients increases 100-fold over the next few decades, the chances of any particular donor being infected would still be less than 1:1,000,000. In some cases, a patient needs a transfusion containing white blood cells. These instances are rare compared to the need for red blood cells and other blood factors. Therefore, restricting donations containing white blood cells to low-BSE-risk areas is only prudent because the possibility of transmission (however small) may be present and the supply of this rare type of donation is not endangered by a restricted blood supply. More research needs to be done before a decision is made that will potentially prevent thousands of Americans from receiving life-saving medical care. Animal studies that test the ability of fractionated red blood cells to transmit BSE or scrapie to uninfected animals must be done to evaluate the real risk of transmission of nvCJD by blood transfusions. To prevent a crisis in blood supply in the unlikely event that the population of nvCJD patients increases dramatically, diagnostic tests must be developed that can detect an infectious dose of nvCJD agent in blood. Medical procedures, including blood transfusion, are not without risk. The increased risk of complications of a transfusion arising due to the transmission of nvCJD by blood transfusion is vanishingly low due to the rarity of the disease, the removal of the pathogen-carrying cells from donated blood and the uncertainty that blood-borne transmission is even possible. Until evidence appears that unambiguously demonstrates that fractionated blood can be a vector for nvCJD transmission, the FDA should not restrict the supply of blood. No doubt the memory of people infected with HIV from transfusions weighs heavily on FDA policymakers, but they must not risk withholding medical treatment from those in need of transfusions to salve their wounded conscience. A doctor would never dissect a living person to harvest organs to save the lives of many others who may need the organs some day. Similarly, the FDA should not endanger the lives of people in need of transfusions to protect others from an epidemic that probably will never take place. Rocco Casagrande, PhD (rocco_casa@yahoo.com), studies security risks associated with prion diseases. He is a scientist at Surface Logix Inc, a Boston-based company developing new tools for drug discovery. This opinion does not necessarily reflect that of Surface Logix. Thanks to R.H. Sprinkle, MD-PhD, for assistance.

Bad Blood Between the FDA and Europe

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