Weigh Pros and Cons of West Nile Screening

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Testing may be justified at centers in areas with high virus activity

 

SAN FRANCISCO—Transplant centers need to weigh the pros and cons of screening solid organs for West Nile virus prior to transplantation, a Canadian researcher said here at the 46th annual Interscience Conference on Antimicrobial Agents and Chemotherapy.

 

Several transplant centers in the United States are considering universal polymerase chain reaction testing for the virus in all donated solid organs. In areas where there are higher rates of West Nile virus infection, this type of testing could help lower the risk of transmission, said Atul Humar, MD, director of transplant infectious diseases at the University of Toronto. In places where transmission rates are consistently very low, however, screening may lead to unnecessary costs and potential harm because of false positive results.

 

“False positives can lead to not using organs that otherwise would have been suitable,” Dr. Humar said. “Another factor that confounds this issue is what type of test to use in the setting of a deceased donor.”

 

Although blood products are universally screened for the virus, he noted, no guidelines call for universal screening of donated kidneys and other solid organs. West Nile virus can be acquired in transplant patients via multiple mechanisms, including blood transfusions, contaminated donor organs, and mosquito bites. Once exposed, transplant patients are much more likely to have rapid onset and lethal disease, which is fueling debate over screening donated organs for the virus.

 

West Nile virus has been bad in some areas in recent years. Some years have been worse than others but the problem is not going to go away,” he said.

 

So far, two multiple-transplant recipients have acquired West Nile virus from an infected donor. In one case, the organ donor was likely infected through a blood transfusion. In the second case, the donor was likely infected from a mosquito bite. Both patients became ill.

 

It is unclear how cost effective it would be to embrace universal testing for West Nile virus in donated organs. Prior to the arrival of screening blood products for West Nile virus, the risk of transfusion-transmitted infection was estimated to be 1 in 30,000, but it may be have been much higher in endemic areas—as high as 1 in 1,000. In the average transplant recipient, the risk of developing severe neuroinvasive disease is estimated to be about 40%.

 

If a community has a great deal of West Nile virus activity in a given year and a transplant program is considering screening donors for the virus, then it will need to consider issues that have not yet been thoroughly addressed, such as available assays, laboratory resources, turn-around time, and medicolegal concerns, Dr. Humar said.

 

The United Network for Organ Sharing only recommends testing of donated organs where there are significant prevalence rates.

 

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