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Blood for transfusion
Results from a pair of studies suggest it is necessary to test for Zika virus in all blood donated in the US, even blood collected outside areas of active Zika transmission.
Last year, the US Food and Drug Administration recommended that all states and US territories screen donated whole blood and blood components for the Zika virus.
Two studies published in Transfusion support that recommendation by revealing the presence of blood donors who tested positive for Zika and may have acquired the infection via travel or sexual contact.
In the first study, researchers screened donor plasma samples using the cobas Zika test. Some of the researchers are employees/contractors of Roche Molecular Systems, Inc., which developed the test.
The study included 358,786 blood donations made in US states. Plasma samples from 23 of the donors were reactive on the first test.
For these cases, the testing lab performed repeat tests with cobas Zika. The lab also simulated minipool testing by diluting a donor sample 1:6 with Zika-negative human plasma. In addition, the reactive samples were sent out for alternate nucleic acid testing and serology testing.
The additional tests suggested 14 of the samples were positive for the Zika virus.
Ten of the 14 donors said they had traveled to an area of active Zika transmission within 90 days of their donation, and 3 of the 10 donors also had a sexual exposure risk. The median time from the end of the donors’ travel to their donation was 25 days (range, 6-71).
Three donors had not traveled to an area of active Zika transmission outside the US, but they lived in Miami-Dade County and were thought to have contracted the virus there.
For the remaining donor, there was no information on travel or sexual exposure risk.
The researchers said minipool testing likely would have identified half of the Zika-positive donations, as only 7 of the 14 donations with probable Zika virus infection were detectable via the simulated minipool testing.
The team also said the estimated specificity of the cobas Zika test was 99.997%.
In the second study, researchers screened donor plasma samples using the Procleix Zika virus assay. Some of the researchers are employees/contractors of Hologic, Inc., and Grifols Diagnostic Solutions, Inc., the companies that co-developed the assay.
The study included 466,834 blood donations in the US (outside of Puerto Rico and Florida). Twenty donor samples were reactive on the initial test.
These 20 samples (and additional samples from these donors) underwent subsequent testing with the Procleix Zika virus assay, real-time polymerase chain reaction, and Zika virus IgG and IgM capture ELISAs.
According to subsequent tests, 5 donors were reactive for Zika virus RNA. All of these donations were collected outside areas of active Zika transmission, but all 5 donors had traveled to areas of active transmission.
The researchers said the estimated specificity of the Procleix Zika virus assay was 99.997%.
The team also reported transfusion of an apheresis platelet donation from 1 of the 5 Zika-positive donors. The recipient of this product did not develop Zika infection, which suggests these units may not be infectious.
However, other researchers previously reported what they believed to be transmission of the Zika virus via platelet transfusion.
