STI Found to Be New Category of High-Risk Organ Donors

Daniel M. Keller, PhD

May 16, 2011

May 16, 2011 (Philadelphia, Pennsylvania) — The epidemiology of certain infections has changed since the US Centers for Disease Control and Prevention (CDC) issued classifications of high-risk organ donors in 1994. Current evidence shows that sexually transmitted infection (STI) might now be considered a high-risk category for transmitting HIV, given its high incidence and prevalence among people with an STI. But it might be possible to drop hemophilia as a risk category, given the less than 1 in 100,000 incidence of HIV today, Lauren Kucirka, ScM, an epidemiologist in the Department of Surgery at the Johns Hopkins University School of Medicine in Baltimore, Maryland, said here at the American Transplant Congress 2011.

The CDC currently considers potential donors to be at high risk on the basis of 7 categories of behavior or circumstances: men who have sex with men, injection drug users, hemophiliacs, commercial sex workers, people who have high-risk sex (meaning sex with people in any of the foregoing groups), people who have been exposed to HIV through blood, and people who are incarcerated.

About 9% of donors from whom at least 1 organ is recovered are classified as high-risk according to CDC criteria, and these organs are 26% more likely to be discarded than organs from donors not considered high risk. Ms. Kucirka told the audience that the CDC guidelines have several limitations, including the fact that they were developed in 1994, before highly active antiretroviral therapy; the fact that they were aimed in part at HIV, but have been extended to hepatitis C virus (HCV); and the fact that they were developed to identify donors at risk for prevalence infection, but the real risk is from incident infection. For example, the prevalence of HIV is high among people with hemophilia who received transfusions in the 1980s, but the incidence of new infections is low now that blood is well screened.

Through a systematic review of the literature on the incidence and prevalence of HIV and HCV from 1995 to 2008 and a meta-analysis, Ms. Kucirka and colleagues investigated potential new high-risk categories. They identified 272 eligible abstracts for HIV estimates and 218 for HCV estimates.

Window Period

Although all donors are tested for infectious diseases, if they are in the "window period" — early after infection but before the infection is detectable — they will have a false-negative test result and might, therefore, transmit an infection to one or more recipients. "The window period using nucleic acid testing for diseases like HIV and hepatitis C is about a week," Ms. Kucirka said.

Using various calculations based on information from the abstracts, the investigators were able to calculate a "risk of window-period infection" for HIV. For the current CDC categories, "the incidence ranged from 2 infections per 100 person-years for injection drug users to less than 1 per 10,000 person-years for hemophiliacs,'" she said.

After reviewing the abstracted data, the authors defined subgroups of the population with a high incidence of HIV or HCV. Body piercings or tattoos did not appear to confer any increased incidence; intranasal cocaine use also showed a low incidence.

"Finally we looked at STI," Ms. Kucirka reported. "We found, among those who were positive for [any] STI, a pooled incidence of 1.7 per 100 person-years, which was similar to the incidence in men who have sex with men and injection drug users, and would result in an expected number of 4.2 window-period HIV infections per 10,000 donors." Compared with their peers from the same study population, people with STIs had about twice the prevalence and twice the relative incidence of a window-period HIV infection.

The "addition of new categories should be approached with caution, particularly in light of the high discard rate when a donor is classified as high risk," Ms. Kucirka advised. Nonetheless, STI could be considered a potential high-risk category, given the high incidence and prevalence of HIV infection in this category. But given the very low incidence among people with hemophilia, this category "could potentially be dropped," she said.

During the question period, an audience member noted that the CDC is formulating new guidelines and will release them for comment soon.

Emily Blumberg, MD, professor of medicine and director of transplant infectious diseases at the University of Pennsylvania in Philadelphia, and chair of the Ad Hoc Disease Transmission Advisory Committee of the Organ Procurement and Transplantation Network, told Medscape Medical News that there is a "real push" to update the guidelines while balancing infectious risk against trying to maximize the number of donor organs available for transplant. "As a community, transplant professionals are committed to providing the safest possible utilization of the greatest number of organs. That's really what's driving all of these policy revisions," she said. Dr. Blumberg was not involved in the study.

"We're operating based on some assumptions that were made in 1994, which are clearly obsolete at this point, inappropriate in some settings, and don't reflect either the available testing or the changing demographics of blood-borne pathogens like HIV and hepatitis C and hepatitis B," Dr. Blumberg said. "We actually still don't really know what constitutes higher risk for blood-borne pathogens, but we need to get a better sense of this because the public perceives this is a tremendous risk."

Transplant professionals have a more realistic, less "sensationalized" view of the risk, she said, noting that since 1987, there have been only 2 transmissions of HIV from deceased donations and 1 transmission from a live donation. "That's a pretty good track record, I think. We're all trying to figure out how to make all of these things even safer," she stressed.

Ms. Kucirka and Dr. Blumberg have disclosed no relevant financial relationships.

American Transplant Congress (ATC) 2011: Concurrent session 79. Presented May 4, 2011.

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