Emerging infectious agents pose new risks for people with bleeding disorders

Feb 16 2006

An international team of scientists, including a hematologist from Thomas Jefferson University in Philadelphia, has concluded that people with bleeding disorders such as hemophilia remain at risk from emerging infectious agents in plasma and blood transfusions. For this reason, recombinant therapies, that is, those produced in the laboratory, must always be an option.

Writing January 21, 2006 in the journal Lancet, hematologist Jamie Siegel, M.D., clinical associate professor of medicine at Jefferson Medical College of Thomas Jefferson University in Philadelphia, Christopher A Ludlam, professor of haematology and coagulation medicine at the Royal Infirmary, Edinburgh, Scotland, UK, and colleagues say that coagulation-factor concentrates (CFC) from the blood plasma, used for individuals with bleeding disorders, are now deemed safe from most known infectious agents, such as hepatitis B and C viruses and HIV, in contrast to two decades ago. But challenges from new agents mean plasma-derived products will continue to remain at risk.

The authors point out that an alternative - recombinant products, which are made by expressing genes for clotting factors in the laboratory tissue culture dish - lessen the likelihood of contamination by infectious agents.

"There will always be emerging pathogens and we won't always know what they are," says Dr. Siegel, who is director of the Hemophilia Center at Thomas Jefferson University Hospital. "We know that these pathogens may be in the blood supply, and if we have a population dependent on plasma derived products, they are always at risk."

She contends that infectious agents called prions, which are behind diseases such as new variant Creutzfeldt-Jakob disease ("Mad Cow disease"), may be the most worrisome of all because they are difficult to detect. She is concerned about them affecting mostly young children, and their effects decades later. "We don't know if we can get rid of prions," she says. "Currently, there is no available method to diagnose and deal with them effectively."

The continued debate about the safety of the blood supply and the use of blood-derived versus artificial products for those with bleeding disorders is under the constant threat of emerging infectious agents. Blood-derived products work better in clotting blood, but carry the caveat of potential exposure to infectious agents in the blood supply. Recombinant clotting products made in the laboratory may not be quite as effective, but are virtually risk-free from contamination. Up until now, decisions on using blood-derived versus recombinant blood products have been left to patients and physicians. Safety studies have not definitively made the case for either.

But Dr. Siegel is concerned. "Today, the doctor reviews treatment options with the patient and together they choose the product to be used." According to Dr. Siegel, Pennsylvania is the first state to have challenged the idea that recombinant products are safer than plasma-derived products for blood clotting disorders. In addition, the state has established a preferred drug list, she says, noting that blood-derived products may cost half the price. For now, all hemophilia drugs are listed as preferred drugs, but she is worried about the long term.

"It means you could create a two-tiered system and medical assistance patients may get plasma-derived products, and potentially not get as good as care as those with private insurance," Dr. Siegel says. "It means they may have limited access to the safest treatments.

Dr. Siegel says that she is more confident in the safety of recombinant products with respect to infectious agents and doesn't want individuals with hemophilia to again be the victims of unsafe blood products as they were in the beginning of the AIDS epidemic in the early 1980s.