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New screening ensures safety of blood products

FROM: DRUG TOPICS; Hospital Practice; May 15

by DOUGLAS PAGE

Each year, approximately 14 million units of whole blood are collected from about eight million volunteer donors. This blood is used to make components that are transfused directly into the more than 3.5 million Americans whose health depends on plasma-derived products.

In the 1980s, the discovery of viral transmission by these plasma-derived products sent panic through the blood-recipient public, as well as through the pharmaceutical industry. In 1987, for instance, an estimated 12,000 patients were infected with HIV through transfusion of contaminated blood products. In San Francisco alone, an estimated 2,135 transfusion recipients were infected with HIV during the seven years before HIV-antibody testing of blood donations began in 1985.

While the fear persists today, new measures recently introduced to screen blood products for HIV and other key viruses may dilute some of the concern. In March, the Food & Drug Administration heard testimony from Aventis Behring, King of Prussia, Pa., about polymerase chain reaction (PCR) screening, one of the latest advancements to help ensure blood product safety. The first U.S. company to screen plasma for the five most feared viruses (HIV, hepatitis A, hepatitis B, hepatitis C, and parvovirus B19), Aventis Behring was asked by the FDA to present data about its use of investigational PCR screening. PCR screening tests blood for the actual presence of virus as opposed to traditional screening methods, which test merely for the body's response to virus.

PCR screening is a form of nucleic acid testing (NAT) designed to detect extremely low levels of viruses by testing for the presence of viral genetic material (DNA and RNA). It is believed to enable detection of viruses at an earlier stage than traditional screening methods (e.g., serology). Serology screening detects either virus proteins or antibodies to virus proteins (the body's response to viral presence). The data presented by Aventis Behring indicate that PCR screening may be valuable in identifying the presence of hepatitis B (HBV) virus in plasma that had already cleared serology tests that screen for HBV surface antigen.

Knowledge of the techniques used to determine the safety of plasma products is important for pharmacists who dispense these therapies to patients. "Anything we can do to ensure the safety of the products we provide our patients is something we want to pursue," said Jeff Binkley, Pharm.D., a clinical pharmacist at Vanderbilt University in Nashville. "This PCR testing, while it's investigational, does provide a more sensitive test than the standard serology test, so that the test to detect the virus is shortened."

Although several manufacturers have committed to exploring the use of NAT to screen source plasma for viruses prior to manufacturing, the process is still considered investigational. The data presented to the FDA's Blood Products Advisory Committee included an analysis of 3.25 million plasma samples that underwent NAT utilizing Aventis Behring's proprietary PCR technology following negative results using traditional serology tests for HBV. Investigators found that 62 samples from 42 donors contained the virus.

"If PCR technology allows you to identify plasma donations containing HBV that were undetected by traditional serology tests, then you have to believe that is a safety advance," said Aventis Behring's Charles Watson, Ph.D., manager of the PCR Laboratory and presenter to the advisory committee. "The data we have compiled suggest that extensive PCR screening is the right thing to do."

Although the study is ongoing, the researchers believe PCR is a critical step toward their objective of ensuring that only the highest quality plasma possible enters the manufacturing process. For the 40 million patients worldwide who rely on plasma-derived products for conditions such as burns, shock, bleeding, and immune disorders, the quality of the products is critical. "I think back to what one of my professors told me in college," said Binkley. "When you're dispensing a drug, you want to pretend the patient is one of your family members. If I were providing this product for one of my family members, I would want as many safety procedures in place as possible."

To answer questions about blood safety generally and PCR screening specifically, the company has launched a campaign to provide information about the plasma product development process. A virtual tour of the purification and production process of plasma products, as well as brochures and a free CD, are available to medical professionals, patients, and their families through the Aventis Behring North America Web site, www.AventisBehring.com/na, or by calling 1-(800) 683-1288.