The American Red Cross' Zika virus screening program so far has detected relatively few blood donations infected with the virus—but has spent roughly $5.3 million per positive test, according to study published Thursday in the New England Journal of Medicine.
Amid the Zika outbreak in 2015 and 2016, FDA recommended that U.S. territories and states screen individual units of donated blood for the Zika virus. In response, the American Red Cross launched an investigational screening program that tests blood donations using transcription-mediated amplification (TMA). The program conducts TMA testing on individual samples as well as through "exploratory minipools."
For the study, researchers examined Zika screenings conducted by the American Red Cross implemented between June 2016 and September 2017. According to STAT News, the program costs about $137 million annually.
During the study period, the program screened 4,325,889 units of blood from 48 states. Of those, the researchers found that 393,713 initially were tested in 24,611 minipools, and none were found to contain Zika. The remaining 3,932,176 donations were tested individually, the researchers wrote. Of those, nine tested positive for the Zika virus, and four of those units appeared to be infectious because they contained both Zika antibodies and the virus. Of the nine units that tested positive for Zika, the researchers said eight likely stemmed from mosquito transmission of the virus.
Overall, the researchers wrote, "On the basis of industry-reported costs of testing and the yield of the tests in our study, the cost of identifying eight mosquito-borne [Zika] infections through individual-unit nucleic acid testing was $5.3 million per [Zika]-positive donation." The researchers concluded, "Screening of U.S. blood donations for [Zika] by individual-donation TMA was costly and had a low yield."
Susan Stramer, senior author of the study and vice president of scientific affairs at the American Red Cross Biomedical Services, said screening blood donations for Zika could cost 50% less if donated blood were tested in small pools instead of by individual units. According to STAT News, the Red Cross screens for several pathogens in blood donations—such as HIV, hepatitis B and C, and West Nile virus—using small pools.
Stramer said, "For Zika, we treat that virus differently than we treat any other virus. So I think the argument we're trying to make is that Zika should be treated just like West Nile or HIV … etc., and not have to test each donation individually. Because it's certainly a waste of resources and a waste of our capacity, which we should be using that for other things."
FDA, which currently recommends that blood supply operators screen blood samples in pools rather than individually, said it does not usually comment on individual studies. The agency also did not state why it has not moved forward with an advisory panel's recommendation in December 2017 to allow blood supply operators to screen donated blood for Zika in pools rather than in individual units. However, FDA said it is considering revising its guidelines for Zika screening.
But Evan Bloch, a pathologist and transfusion medicine specialist at Johns Hopkins School of Medicine, and colleagues in a commentary published in the New England Journal of Medicine wrote that it is more difficult to scale back or eliminate a blood screening program than it is to implement one. Bloch said, "When I initially started writing the paper, I really thought: 'Yes, this is a stupid policy.' I was very kind of black and white about it." However, he said, "I began to realize that if you were transported back to like the early '80s with HIV, had they been this aggressive in their response, you might have had a very different outcome with HIV and the blood supply" (Branswell, STAT News, 5/9; Stobbe, AP/ABC News, 5/9; Norton, HealthDay, 5/9; Saá et al., New England Journal of Medicine, 5/10).
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