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Efficacy of Minipool Testing of Blood Donors for Zika Virus

Zika virus has been a major concern in transfusion medicine due to the large proportion of asymptomatic infections and the severe clinical consequences for patients if the virus is transmitted by blood transfusion. In 2016, the American Red Cross (ARC) introduced screening of blood donors for Zika Virus in high-risk U.S. states. This process began in June 2016, testing donor blood samples in 16-member minipools. Subsequently, a revised FDA guidance required all U.S. donations be tested via individual donation transcription-mediated amplification (ID-TMA). The ARC has performed an analysis of 15 months of testing donors for Zika virus.

Of the 4,325,889 donations screened, 9 donors were confirmed to be positive. Four of these 9 donors were Zika IgM antibody negative, indicating that these donors were in the window period prior to seroconversion. Confirmed positive donations in ID-TMA were tested again by TMA in simulated minipools. They were found to be 100% positive for the three donors who could be tested and who were identified as being Zika IgM negative.

Confirmed positive donors consented to follow-up with further testing. The longest period of Zika RNA detection was 66 days in plasma and 154 days in red cells in the same donor.

The cost of testing by minipool was estimated to be $6 per donation. The cost rose to $10 for ID-TMA. The total cost over the 15-month study was almost $42 million. The total annual cost was calculated to be $5.3 million for each RNA positive donor identified.


Saa, P., et al. (2018). Investigational Testing for Zika Virus among U.S. Blood Donors. N Engl J Med 378(19): 1778-1788.

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