Monday, March 21, 2011

Transfusion - Bloodborne infection risk

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As long as blood has been donated from one person to another, risk of transmitting pathogens has existed.

By Jill Hoffman
Posted on: March 21, 2011
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As long as the field of transfusion medicine has existed, and blood has been donated from one person to another, risk of transmission of pathogens and their resulting diseases has existed.
The primary diseases at issue are hepatitis B and C, HIV/AIDS, Human T-lymphotropic virus (HTLV), syphilis, West Nile virus and Chagas disease, said Roger Y. Dodd, PhD, vice president, Research and Development, American Red Cross, Holland Laboratory, Rockville, MD.
"The ones that have been more pervasive are probably the ones under the best control right now," he said.

ScreeningTraditionally three tests have been used to screen for infections, although two are primarily used.

Antibody tests investigate the immune system's response to infection; they test for HIV, hepatitis B and C, HTLV, syphilis and Chagas disease. In some cases, viral antigen tests are used, particularly for hepatitis B.

Nucleic acid tests (NATs) look for genetic material of the virus and are often used for HIV, West Nile virus, hepatitis C, and more recently in the U.S., hepatitis B.
Surrogate tests, which are not disease specific, look for other related conditions. For example, Dr. Dodd mentioned an elevated liver enzyme test used in the past to look for evidence of liver disease and hepatitis B and C.
"I wouldn't put a lot of emphasis on surrogate testing," Dr. Dodd added.
Recent StudiesIn a recent epublication of Transfusion, authors studied risk of HIV and HCV infections among U.S. blood donors since introduction of NAT.1 Researchers found for HIV a small increase in incidence-primarily among 16- to 19-year-old, male African American donors-between 2007 and 2008. A relatively small increase in HCV was also noted, although Dr. Dodd, a co-author of the study, says prevalence for both viruses has remained constant or decreased significantly.

"We keep up our surveillance and if we see trends, we have to think of ways to improve the situation," Dr. Dodd said.

A recent Transfusion article looking at bloodborne infection risk among a growing number of apheresis collections-where donor blood is passed through an apparatus separating particular components-at the American Red Cross Blood Services between 2004 and 2008 found risk was low, although an upward trend in viral marker frequency among donations was attributable to changes in the structure of the donor population, mainly among first-time, male R2 (automated red cell) donors.2

Dr. Dodd, a co-author of the study, explained that most apheresis collections involve platelets from experienced donors, although labs are increasingly collecting two units of red cells.
"As we increased the proportion of donations collected for red cells we increased the number of first-time donors that tended to have a higher frequency of infection," Dr. Dodd said. "But although there appeared to be a change in the frequency of infection, it really was an artifact of the way we were grouping our donors and the structure of that population. So the real message there was that the risk was very low."

Dr. Dodd said the paper highlights the need to understand the dynamics of a particular donor population to make sense of its infection frequency.
DevelopmentsPathogen reduction or inactivation technology prevents pathogens from replicating and causing disease following transfusion and is something many people in the field are looking to prevent transfusion-transmitted infections.3
The U.S. does not have an FDA-approved pathogen inactivation process for blood transfusion products or blood components (plasma, platelets or red cells), although several methods for plasma and platelets are routinely in use in Europe. Therapeutic plasma products are often treated with solvents, detergents and other heating and filtration methods. "Those products have for many years been very safe," Dr. Dodd said.

The field also looks forward to increasingly sensitive tests to screen for traditional and new and emerging infections. Dr. Dodd pointed out that NAT has only been performed in the U.S. for HIV and HCV samples since 1999 and since 2003 for West Nile virus.

A new transfusion-transmitted infection on the world's stage is Dengue virus or "break-bone fever." The mosquito-transmitted virus is prevalent in the tropics and "could easily get a foothold in this country," Dr. Dodd said. In the U.S., the Babesia parasite is a tick-borne infection found primarily in the Northeast and upper Midwest that is rising in frequency and spreading in geographic area.

"If you look at the big scene of things, the risk of known transfusion-transmitted infections has been reduced to very low levels-one in a million or less for HCV and HIV and not quite that low but at comparable levels for hepatitis B, and this used to be a really serious and frequent outcome of transfusion," Dr. Dodd said. "I think the message is the blood supply is very safe."
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Jill Hoffman is on staff at ADVANCE.
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References
Zou S, Dorsey KA, Notari EP, Foster GA, Dodd RY, et al. Prevalence, incidence, and residual risk of human immunodeficiency virus and hepatitis C virus infections among United States blood donors since the introduction of nucleic acid testing. Transfusion 2010, Mar 12.
Zou S, Musavi F, Notari EP, Stramer SL, Dodd RY. Prevalence, incidence, and residual risk of major blood-borne infections among apheresis collections to the American Red Cross Blood Services, 2004 through 2008. Transfusion 2010, Mar 12.
Sheppard CA, Josephson CD, Hillyer CD. Bacterial Contamination of Platelets for Transfusion: Pathogen Reduction (Inactivation). WebMD LLC. Available at: www.medscape.com/viewarticle/517753_9.
Last accessed June 22, 2010.
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